US20050154168A1 - Polyethylene films - Google Patents

Polyethylene films Download PDF

Info

Publication number
US20050154168A1
US20050154168A1 US11/007,863 US786304A US2005154168A1 US 20050154168 A1 US20050154168 A1 US 20050154168A1 US 786304 A US786304 A US 786304A US 2005154168 A1 US2005154168 A1 US 2005154168A1
Authority
US
United States
Prior art keywords
film
polyethylene composition
molecular weight
less
polyethylene
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
US11/007,863
Other versions
US7090927B2 (en
Inventor
Porter Shannon
Rakesh Kumar
Pradeep Shirodkar
Fred Ehrman
Mark Davis
Keith Trapp
Dongming Li
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Individual filed Critical Individual
Priority to US11/007,863 priority Critical patent/US7090927B2/en
Publication of US20050154168A1 publication Critical patent/US20050154168A1/en
Application granted granted Critical
Publication of US7090927B2 publication Critical patent/US7090927B2/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

Links

Images

Classifications

    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08LCOMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L23/00Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
    • C08L23/02Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
    • C08L23/04Homopolymers or copolymers of ethene
    • C08L23/08Copolymers of ethene
    • C08L23/0807Copolymers of ethene with unsaturated hydrocarbons only containing more than three carbon atoms
    • C08L23/0815Copolymers of ethene with aliphatic 1-olefins
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08JWORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J5/00Manufacture of articles or shaped materials containing macromolecular substances
    • C08J5/18Manufacture of films or sheets
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08FMACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F210/00Copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
    • C08F210/04Monomers containing three or four carbon atoms
    • C08F210/08Butenes
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08FMACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F210/00Copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
    • C08F210/16Copolymers of ethene with alpha-alkenes, e.g. EP rubbers
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08JWORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2323/00Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
    • C08J2323/02Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
    • C08J2323/04Homopolymers or copolymers of ethene
    • C08J2323/06Polyethene
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08JWORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2323/00Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
    • C08J2323/02Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
    • C08J2323/04Homopolymers or copolymers of ethene
    • C08J2323/08Copolymers of ethene
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08LCOMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L2205/00Polymer mixtures characterised by other features
    • C08L2205/02Polymer mixtures characterised by other features containing two or more polymers of the same C08L -group
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08LCOMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L2205/00Polymer mixtures characterised by other features
    • C08L2205/02Polymer mixtures characterised by other features containing two or more polymers of the same C08L -group
    • C08L2205/025Polymer mixtures characterised by other features containing two or more polymers of the same C08L -group containing two or more polymers of the same hierarchy C08L, and differing only in parameters such as density, comonomer content, molecular weight, structure
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08LCOMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L2666/00Composition of polymers characterized by a further compound in the blend, being organic macromolecular compounds, natural resins, waxes or and bituminous materials, non-macromolecular organic substances, inorganic substances or characterized by their function in the composition
    • C08L2666/02Organic macromolecular compounds, natural resins, waxes or and bituminous materials
    • C08L2666/04Macromolecular compounds according to groups C08L7/00 - C08L49/00, or C08L55/00 - C08L57/00; Derivatives thereof
    • C08L2666/06Homopolymers or copolymers of unsaturated hydrocarbons; Derivatives thereof
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00Stock material or miscellaneous articles
    • Y10T428/13Hollow or container type article [e.g., tube, vase, etc.]
    • Y10T428/1334Nonself-supporting tubular film or bag [e.g., pouch, envelope, packet, etc.]
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00Stock material or miscellaneous articles
    • Y10T428/13Hollow or container type article [e.g., tube, vase, etc.]
    • Y10T428/1334Nonself-supporting tubular film or bag [e.g., pouch, envelope, packet, etc.]
    • Y10T428/1338Elemental metal containing
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00Stock material or miscellaneous articles
    • Y10T428/13Hollow or container type article [e.g., tube, vase, etc.]
    • Y10T428/1334Nonself-supporting tubular film or bag [e.g., pouch, envelope, packet, etc.]
    • Y10T428/1345Single layer [continuous layer]
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00Stock material or miscellaneous articles
    • Y10T428/13Hollow or container type article [e.g., tube, vase, etc.]
    • Y10T428/1352Polymer or resin containing [i.e., natural or synthetic]
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00Stock material or miscellaneous articles
    • Y10T428/13Hollow or container type article [e.g., tube, vase, etc.]
    • Y10T428/1352Polymer or resin containing [i.e., natural or synthetic]
    • Y10T428/1397Single layer [continuous layer]
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00Stock material or miscellaneous articles
    • Y10T428/31504Composite [nonstructural laminate]
    • Y10T428/31855Of addition polymer from unsaturated monomers
    • Y10T428/31938Polymer of monoethylenically unsaturated hydrocarbon

Definitions

  • the present invention relates to polyethylene films, and more particularly, relates to bimodal polyethylene compositions useful in films having a low level of film impurities and enhanced processability.
  • High density bimodal polyethylene compositions and in particular, high density “bimodal” or “multimodal” polyethylenes (“bHDPE”), are known to be useful in making films suitable for a variety of commercial products such as films, pipes, blow molding, etc.
  • bHDPE high density polyethylenes
  • the costs of producing such compositions is a disadvantage—being relatively high—as most bHDPEs are produced in two stages or more, and/or in two or more staged reactors such as the processes of Dow, Basell, Borealis and Mitsui .
  • Such commercial polymerization systems are reviewed in, for example, 2 M ETALLOCENE -B ASED P OLYOLEFINS 366-378 (John Scheirs & W. Kaminsky, eds. John Wiley & Sons, Ltd. 2000).
  • bHDPEs can present further commercial problems.
  • film cooling upon extrusion of the polyethylene, is a limiting factor in film production, especially for extrusion of high density polyethylene, such as described in F ILM E XTRUSION M ANUAL , P ROCESS , M ATERIALS , P ROPERTIES , pp. 497 (TAPPI, 1992).
  • One solution to this problem is to operate at a desirably low melt temperature.
  • melting may be uneven, and/or relatively high melt temperatures must be maintained for the given resin.
  • high back pressures can be maintained, but this can lead to other problems, and consumes more energy.
  • What would be desirable is a bHDPE that can be extruded at a rapid rate at a relatively low melt temperature, using lower extruder motor loads, while maintaining high film quality.
  • Single reactor systems may offer such a cost advantage. While single reactor systems have been described as capable of producing bimodal polyethylenes for film applications, such as described by H-T. Liu et al. in 195 M ACROMOL . S YMP . 309-316 (July, 2003), those films must still match the quality and processability of current dual-reactor derived polyethylene films for commercial viability.
  • the present invention in one aspect is directed towards such a film, as the inventors have found that a certain balance of polymer properties can meet these commercial needs to produce polyethylene films suitable for cast, blown and other film products; and further, that it is possible to achieve these ends using single-reactor produced polyethylene compositions.
  • the present invention provides a film comprising a polyethylene composition, preferably a bimodal polyethylene, possessing a density of between 0.940 and 0.970 g/cm 3 , and an I 21 value of less than 20 dg/min; characterized in that the polyethylene composition extrudes at a melt temperature, T m , that satisfies the following relationship: T m ⁇ 235 ⁇ 3.3 (I 21 ); wherein the polyethylene composition is extruded at a specific throughput of from 1 (0.454 kg/hr/rpm) to 1.5 lbs/hr/inch (0.681 kg/hr/rpm), and wherein the film has a gel count of less than 100.
  • the present invention provides a film comprising a polyethylene composition, preferably a bimodal polyethylene, the polyethylene composition comprising a high molecular weight component having a weight average molecular weight of greater than 50,000 amu and a low molecular weight component having a weight average molecular weight of less than 40,000 amu or less than 20,000 amu or less than 15,000 amu or less than 12,000 amu; the polyethylene composition possessing a density of between 0.940 and 0.970 g/cm 3 , and an I 21 value of less than 20 dg/min and a Mw/Mn value of from greater than 30 or 35 or 40; characterized in that the film has a gel count of less than 100.
  • the polyethylene compositions useful for the films of the invention are produced in a single reactor, preferably a single continuous gas phase reactor.
  • FIGS. 1 and 2 are graphical representations of melt index (I 21 ) values of the inventive examples 1 and 2 ( ⁇ ) and comparative examples ( ⁇ , ⁇ ) versus motor loads and pressures upon extrusion to form a film of 0.5 mil gauge, extruded at a specific throughput of from 1.84 to 1.90 lbs/hr/rpm;
  • FIGS. 3, 4 and 5 are graphical representations of data obtained from GPC comparing the molecular weight profile of the comparative example 1 (—) with each of inventive examples 3, 4 and 5 (- - - - - ); and
  • FIGS. 6 and 7 are graphical representations of melt index (I 21 ) values of the inventive examples 3 and 5 through 9 ( ⁇ ) and comparative examples (numbered open circles) versus motor loads and pressures upon extrusion to form a film of 0.5 mil gauge, extruded at a specific throughput of from 1.16 to 1.20 lbs/hr/rpm.
  • the present invention is to a film comprising a polyethylene composition, the polyethylene composition in one embodiment comprising a high molecular weight component and a low molecular weight component and, in a particular embodiment, displaying a multimodal or bimodal GPC profile.
  • the polyethylene composition has improved processing properties as exhibited by a decreased extruder motor load (or power consumption) relative to other polyethylene resins of similar density and flow index (I 21 ). Further characteristic of the invention is the high specific throughput capabilities at advantageously low melt temperatures.
  • the films described herein possess these improved processing properties while maintaining a high film quality, as exemplified by low gel content, while maintaining the strength, flexibility and impact strength comparable to polyethylenes of similar density and I 21 .
  • film includes skins, sheets, or membranes of a thickness of from less than 1000 ⁇ m, more preferably from less than 500 ⁇ m thickness, and even more preferably less than 200 ⁇ m, and most preferably from less than 100 ⁇ m, and includes films fabricated by any process known in the art such as by casting or blowing techniques—oriented or not—from an extruded or calendered, preferably extruded, polyethylene as defined herein, and the use of which can include any number of functions such as wrapping, protecting, packaging, bagging, coating, co-extrusion with other materials; and further, may have any commercially desirable dimensions of width, length, etc.
  • the films of the present invention are not limited to transparent films, and may be opaque or translucent or transparent, preferably transparent, and have other properties as defined herein.
  • the films of the present invention may be co-extruded with or otherwise secured to other sheets/structures, etc. to form structures of thickness greater than 1000 ⁇ m.
  • One aspect of the invention is to a film comprising a polyethylene composition possessing a density of between 0.940 and 0.970 g/cm 3 , and an I 21 value of from 4 to 20 dg/min; characterized in that the polyethylene composition extrudes at a melt temperature, T m , that satisfies the following relationship (I): T m ⁇ 235 ⁇ 3.3( I 21 ) (I) wherein the polyethylene composition is extruded at a specific throughput of from 1 (0.454 kg/hr/rpm) to 1.5 lbs/hr/rpm (0.681 kg/hr/rpm), and wherein the film has a gel count of less than 100.
  • the value “I 21 ” is understood to be multiplied by the number “3.3”.
  • the melt temperature is described by the relationship T m ⁇ 240 ⁇ 3.3 (I 21 ); and in another embodiment, T m ⁇ 240 ⁇ 3.5 (I 21 ); and in yet another embodiment, T m ⁇ 235 ⁇ 3.5 (I 21 ).
  • the melt temperature is the temperature at the downstream end of the mixing zone of the extruder used in processing the polyethylene composition to form the films of the invention. In this aspect of the invention, the melt temperatures are determined from an extrusion line suitable to form the film as described herein.
  • the polyethylene composition can be described as extruding at a specific throughput of from 1.00 lbs polyethylene/hr/rpm (0.454 kg/hr/rpm) to 1.45 lbs polyethylene/hr/rpm (0.648 kg/hr/rpm) at a melt temperature T m satisfying the equation T m ⁇ 235 ⁇ 3.3 (I 21 ).
  • the polyethylene composition extrudes at a specific throughput of from 1.00 lbs polyethylene/hr/rpm (0.454 kg/hr/rpm) to 1.40 lbs polyethylene/hr/rpm (0.636 kg/hr/rpm) at a melt temperature T m satisfying the equation T m ⁇ 235 ⁇ 3.3 (I 21 ).
  • the polyethylene composition extrudes at a specific throughput of from 1.00 lbs polyethylene/hr/rpm (0.454 kg/hr/rpm) to 1.30 lbs polyethylene/hr/rpm (0.590 kg/hr/rpm) at a melt temperature T m satisfying the equation T m ⁇ 235 ⁇ 3.3 (I 21 ).
  • the lower specific throughput limit is 1.10 lbs polyethylene/hr/rpm (0.499 kg/hr/rpm).
  • Examples of desirable melt temperatures T m for the polyethylene compositions of the present invention are values less than 206° C. or 204° C. or 202° C. or 200° C. or 198° C. or 196° C. or 190° C. or 188° C. or 186° C. or 184° C. or 182° C. or 180° C. or 179° C., and in another embodiment, a melt temperature of at least 170° C. or at least 175° C. In another embodiment, the lower melt temperature limit is the minimum melt temperature required to obtain films described herein at the specific throughputs or specific die rates described herein.
  • the improved extrusion properties of the films herein can be described in terms of the specific die rates; in a particular embodiment, the advantageous die rates claimed herein are maintained in a 50 mm grooved feed extruder with an L/D of 21:1 in a particular embodiment.
  • the film of the invention is formed by extruding the polymer composition temperature at a melt temperature, T m , that satisfies the following relationship T m ⁇ 235 ⁇ 3.3 (I 21 ), at a specific die rate of from between 10 and 20 pounds of polymer per hour per inch of die circumference (0.179 to 0.357 kg/hr/mm), and in another embodiment at a specific die rate of from between 10 and 15 pounds of polymer per hour per inch of die circumference (0.179 to 0.268 kg/hr/mm).
  • the melt temperatures are determined from an extrusion line suitable to form the film as described herein.
  • the films of the present invention can be described as having improved melt temperatures compared to prior art bHDPEs of I 21 from 4 to 20 dg/min, regardless of the method of its manufacture or the method of the manufacture of the present polyethylene compositions used to form the films of the invention.
  • the melt temperature of the polyethylene compositions used to make the films of the invention will have values from 2 to 20° C. lower than that for prior art bHDPEs at the same (within +2 to ⁇ 3 units) of I 21 .
  • Another aspect of the invention is to a film comprising a polyethylene composition possessing a density of between 0.940 and 0.970 g/cm 3 , and an I 21 value of from 4 to 20 dg/min; characterized in that the polyethylene composition extrudes at a melt temperature, T m , that is from 2 or 4 to 10 or 20° C. less than polyethylene compositions of similar density and I 12 , range produced in a dual or multiple-reactor process, and extruded under the same conditions, further characterized in that the film has a gel count of less than 100.
  • T m melt temperature
  • Such dual or multi-stage and -reactor processes are know in the art such as described by FP. Alt et al. in 163 M ACROMOL . S YMP .
  • multi-reactor polyethylene compositions refers to polyethylene compositions produced from a staged process comprising the use of two or more reactors in tandem, or to the use of one reactor that is operated in a staged manner, as described in those references above.
  • the melt temperature of the inventive film is compared to the “multi-reactor polyethylene composition” having an I 21 value within ⁇ 3 dg/min, more preferably within ⁇ 2 dg/min, and even more preferably within ⁇ 1 dg/min.
  • the film is described as comprising a polyethylene composition, the polyethylene composition comprising a high molecular weight component having a weight average molecular weight of greater than 50,000 amu and a low molecular weight component having a weight average molecular weight of less than 40,000 amu or less than 20,000 amu or less than 15,000 amu or less than 12,000 amu; the polyethylene composition possessing a density of between 0.940 and 0.970 g/cm 3 , and an I 21 value of less than 20 dg/min and a Mw/Mn value of from greater than 30 or 35 or 40; characterized in that the film has a gel count of less than 100.
  • Other characteristics of the polyethylene composition may be further elucidated as described herein.
  • the quality of the films of the present invention can be characterized by the gel count, as described herein.
  • the films have a gel count of less than 100 in one embodiment, and a gel count of less than 60 in another embodiment, and a gel count of less than 50 in another embodiment, and a gel count of less than 40 in yet another embodiment, and a gel count of less than 35 in yet another embodiment.
  • the films of the present invention have an FAR value of greater than +20 in one embodiment, and greater than +30 in another embodiment, and greater than +40 in yet another embodiment.
  • the films of the present invention can be formed with a gauge variation of from less than 16% of the total thickness in one embodiment, and less than 13% in another embodiment, and from less than 10% in yet another embodiment.
  • the polyethylene composition used to make the films of the present invention can be extruded at lower power levels and lower pressure, for a given specific throughput and melt temperature, than previously known.
  • the polyethylene compositions of the present invention can be extruded at from 1 to 10% lower motor load relative to comparable bimodal polyethylene compositions having, the comparison between resins having a density of between 0.940 and 0.970 g/cm 3 , and an I 21 value of less than 20 dg/min.
  • the improvement is from 2 to 5% lower motor load relative to comparable bimodal polyethylene compositions.
  • the polyethylene compositions of the invention having the properties described herein extrude at a motor load of less than 80% the maximum motor load in one embodiment, and less than 77% the maximum motor load in another embodiment, and less than 75% the maximum motor load in yet another embodiment, and between 66 and 80% maximum motor load in yet another embodiment, and between 70 and 77% maximum motor load in yet another embodiment, wherein a desirable range may comprise any combination of any upper % limit with any lower % limit described herein.
  • the films of the present invention possess properties suitable for commercial use.
  • the films of the invention have an MD Tensile strength of from 9,000 to 15,000 psi and a TD Tensile strength of from 9,000 to 15,000 psi in one embodiment; and an MD Tensile elongation of from 200 to 350% and TD Tensile elongation of from 200 to 350% in another embodiment, and an MD Elmendorf Tear value of from 10 to 30 g/mil in and a TD Elmendorf Tear value of from 20 to 60 g/mil in yet another embodiment; and a dart impact (F50) of greater than 150 g in one embodiment, and greater than 170 g in another embodiment.
  • F50 dart impact
  • the polyethylene composition used to produce the films is preferably free of “hard foulant” material.
  • These “hard foulants” are zones of inhomogeneous material within the polyethylene composition matrix that have distinct characteristics.
  • the hard gels have a melting point (DSC) of from 125° C. to 133° C., and from 126° C. to 132° C.
  • the hard gels have a I 21 of less than 0.5 dg/min in one embodiment, and less than 0.4 dg/min in another embodiment; and also have an ⁇ (0.1 rad/sec at 200° C.) value of from greater than 1000 Mpoise in one embodiment, and greater than 1200 Mpoise in another embodiment; wherein the hard gels can be characterized by any one or combination of these features.
  • free of hard foulant material it is meant that the hard gels are present, if at all, in an amount no greater than 1 wt % by weight of the total polyethylene composition in one embodiment, and less than 0.01 wt % in another embodiment, and less than 0.001 wt % in yet another embodiment.
  • any desirable method of olefin polymerization for example, gas phase, slurry phase or solution polymerization process—that is known for the polymerization of olefins to form polyolefins is suitable for making the polyethylene composition suitable for the films of the present invention.
  • two or more reactors in series are used, such as, for example, a gas phase and slurry phase reactor in series, or two gas phase reactors in series, or two slurry phase reactors in series.
  • a single reactor preferably, a single gas phase reactor is used.
  • this latter embodiment of the present invention comprises incorporating a high molecular weight (“HMW”) polyethylene into a low molecular weight (“LMW”) polyethylene, simultaneously in a single reactor, to form the polyethylene composition, in the presence of polymerizable monomers and a bimetallic catalyst composition.
  • the “polyethylene composition” in one embodiment is a bimodal polyethylene composition, wherein from greater than 80 wt %, preferably greater than 90% of the monomer derived units of the composition are ethylene and the remaining monomer units are derived from C 3 to C 12 olefins and diolefins, described further herein.
  • the LMW polyethylene and HMW polyethylene are incorporated into one another either sequentially or simultaneously, preferably simultaneously from one, two or more reactors of any suitable description; and are incorporated into one another simultaneously in a single polymerization reactor in a particular embodiment.
  • the polymerization reactor used to make the polyethylene composition is a fluidized-bed, gas phase reactor such as disclosed in U.S. Pat. Nos. 4,302,566, 5,834,571, and 5,352,749 typically comprising at least one reactor, only one reactor in a particular embodiment.
  • the LMW polyethylene is a polyethylene homopolymer or copolymer comprising from 0 to 10 wt % C 3 to C 10 ⁇ -olefin derived units, and more particularly, a homopolymer of ethylene or copolymer of ethylene and 1-butene, 1-pentene or 1-hexene derived units.
  • the LMW polyethylene can be characterized by a number of factors. The weight average molecular weight of the LMW polyethylene ranges from less than 50,000 amu in one embodiment, and other embodiments are described further herein.
  • the HMW polyethylene is a polyethylene homopolymer or copolymer comprising from 0 to 10 wt % C 3 to C 10 ⁇ -olefin derived units, and more particularly, a homopolymer of ethylene or copolymer of ethylene and 1-butene, 1-pentene or 1-hexene derived units.
  • the weight average molecular weight of the HMW polyethylene ranges from greater than 50,000 amu in one embodiment, and other embodiments as described further herein.
  • the polyethylene composition of the invention, comprising at least the HMW and LMW polymers, can also be described by any number of parameters as described herein.
  • the films of the present invention can be produced by any suitable catalyst composition that provides for the production of the polyethylene compositions and films described herein.
  • the films are produced from polyethylene compositions produced from a polymerization process using one class of catalyst compounds, or a combination of two or more of a similar class of compounds in another embodiment, or a combination of two or more of differing classes of catalyst compounds in yet another embodiment.
  • the films comprising the polyethylene compositions described herein are produced in a polymerization process utilizing a bimetallic catalyst composition.
  • Such bimetallic catalyst compositions comprise at least two, preferably two, Group 3 to Group 10 metal-containing compounds, both of which may be the same or different metal with similar or differing coordination spheres, patterns of substitution at the metal center or ligands bound to the metal center.
  • suitable olefin polymerization catalysts include metallocenes, Ziegler-Natta catalysts, metal-amido catalysts as disclosed in, for example, U.S. Pat. Nos. 6,593,438; 6,380,328, U.S. Pat. No. 6,274,684, U.S. Pat. No.
  • the bimetallic catalyst composition is a combination of two or more of the same class of catalyst compounds.
  • the bimetallic catalyst composition useful in making the polymer compositions described herein comprise a metallocene and a titanium-containing Ziegler-Natta catalyst, an example of which is disclosed in U.S. Pat. No. 5,539,076, and WO 02/090393, each incorporated herein by reference.
  • the catalyst compounds are supported, and in a particular embodiment, both catalyst components are supported with a “primary” activator, alumoxane in a particular embodiment, the support in a particular embodiment being an inorganic oxide support.
  • a metallocene catalyst component as part of the bimetallic catalyst composition, produces the LMW polyethylene of the polyethylene composition useful for making the films.
  • the metallocene catalyst compounds as described herein include “full sandwich” compounds having two Cp ligands (cyclopentadienyl and ligands isolobal to cyclopentadienyl) bound to at least one Group 3 to Group 12 metal atom, and one or more leaving group(s) bound to the at least one metal atom.
  • the Cp ligand(s) are selected from the group consisting of substituted and unsubstituted cyclopentadienyl ligands and ligands isolobal to cyclopentadienyl, non-limiting examples of which include cyclopentadienyl, indenyl, fluorenyl and other structures.
  • these compounds will be referred to as “metallocenes” or “metallocene catalyst components”.
  • the metal atom “M” of the metallocene catalyst compound is selected from the group consisting of Groups 4, 5 and 6 atoms in one embodiment, and a Ti, Zr, Hf atoms in yet a more particular embodiment, and Zr in yet a more particular embodiment.
  • the Cp ligand(s) form at least one chemical bond with the metal atom M to form the “metallocene catalyst compound”.
  • the metallocene catalyst components of the invention are represented by the formula (II): Cp A Cp B MX n (II) wherein M is as described above; each X is bonded to M; each Cp group is chemically bonded to M; and n is 0 or an integer from 1 to 4, and either 1 or 2 in a particular embodiment.
  • the ligands represented by Cp A and CP B in formula (II) may be the same or different cyclopentadienyl ligands or ligands isolobal to cyclopentadienyl, either or both of which may contain heteroatoms and either or both of which may be substituted by a group R.
  • Cp A and Cp B are independently selected from the group consisting of cyclopentadienyl, indenyl, tetrahydroindenyl, fluorenyl, and substituted derivatives of each.
  • each Cp A and Cp B of formula (II) may be unsubstituted or substituted with any one or combination of substituent groups R.
  • substituent groups R as used in structure (II) as well as ring substituents in structure (II) include hydrogen radicals, C 1 to C 6 alkyls, C 2 to C 6 alkenyls, C 3 to C 6 cycloalkyls, C 6 to C 10 aryls or alkylaryls, and combinations thereof.
  • Each X in the formula (II) and (III) is independently selected from the group consisting of halogen ions (fluoride, chloride, bromide), hydrides, C 1 to C 12 alkyls, C 2 to C 12 alkenyls, C 6 to C 12 aryls, C 7 to C 20 alkylaryls, C 1 to C 12 alkoxys, C 6 to C 16 aryloxys, C 7 to C 18 alkylaryloxys, C 1 to C 12 fluoroalkyls, C 6 to C 12 fluoroaryls, and C 1 to C 12 heteroatom-containing hydrocarbons and substituted derivatives thereof in a particular embodiment; and fluoride in yet a more particular embodiment.
  • halogen ions fluoride, chloride, bromide
  • hydrides C 1 to C 12 alkyls, C 2 to C 12 alkenyls, C 6 to C 12 aryls, C 7 to C 20 alkylaryls, C 1 to C 12 alkoxys
  • the metallocene catalyst component includes those of formula (I) where Cp A and Cp B are bridged to each other by at least one bridging group, (A), such that the structure is represented by formula (III): Cp A (A)Cp B MX n (III)
  • bridged metallocenes These bridged compounds represented by formula (III) are known as “bridged metallocenes”.
  • Cp A , Cp B , M, X and n in structure (III) are as defined above for formula (II); and wherein each Cp ligand is bonded to M, and (A) is chemically bonded to each Cp.
  • Non-limiting examples of bridging group (A) include divalent hydrocarbon groups containing at least one Group 13 to 16 atom, such as but not limited to at least one of a carbon, oxygen, nitrogen, silicon, aluminum, boron, germanium and tin atom and combinations thereof; wherein the heteroatom may also be C 1 to C 12 alkyl or aryl substituted to satisfy neutral valency.
  • a Ziegler-Natta catalyst component as part of the bimetallic catalyst composition, produces the HMW polyethylene of the polyethylene composition useful in making the films of the present invention.
  • Ziegler-Natta catalyst compounds are disclosed generally in Z IEGLER C ATALYSTS 363-386 (G. Fink, R. Mulhaupt and H. H. Brintzinger, eds., Springer-Verlag 1995); and RE 33,683.
  • Such catalysts include those comprising Group 4, 5 or 6 transition metal oxides, alkoxides and halides, and more particularly oxides, alkoxides and halide compounds of titanium, zirconium or vanadium in combination with a magnesium compound, internal and/or external electron donors (alcohols, ethers, siloxanes, etc.), aluminum or boron alkyl and alkyl halides, and inorganic oxide supports.
  • the Ziegler-Natta catalyst is combined with a support material, either with or without the metallocene catalyst component.
  • the Ziegler-Natta catalyst component can be combined with, placed on or otherwise affixed to a support in a variety of ways. In one of those ways, a slurry of the support in a suitable non-polar hydrocarbon diluent is contacted with an organomagnesium compound, which then dissolves in the non-polar hydrocarbon diluent of the slurry to form a solution from which the organomagnesium compound is then deposited onto the carrier.
  • the organomagnesium compound can be represented by the formula RMgR′, where R′ and R are the same or different C 2 -C 12 alkyl groups, or C 4 -C 10 alkyl groups, or C 4 -C 8 alkyl groups.
  • the organomagnesium compound is dibutyl magnesium.
  • Suitable transition metal compounds are compounds of Group 4 and 5 metals that are soluble in the non-polar hydrocarbon used to form the silica slurry in a particular embodiment.
  • Non-limiting examples of suitable Group 4, 5 or 6 transition metal compounds include, for example, titanium and vanadium halides, oxyhalides or alkoxyhalides, such as titanium tetrachloride (TiCl 4 ), vanadium tetrachloride (VCl 4 ) and vanadium oxytrichloride (VOCl 3 ), and titanium and vanadium alkoxides, wherein the alkoxide moiety has a branched or unbranched alkyl group of 1 to 20 carbon atoms, in a particular embodiment from 1 to 6 carbon atoms. Mixtures of such transition metal compounds may also be used.
  • TiCl 4 or TiCl 3 is the starting transition metal compound used to form the magnesium-containing Ziegler-Natta catalyst.
  • the Ziegler-Natta catalyst is contacted with an electron donor, such as tetraethylorthosilicate (TEOS), an ether such as tetrahydrofuran, or an organic alcohol having the formula R′′OH, where R′′ is a C 1 -C 12 alkyl group, or a C 1 to C 8 alkyl group, or a C 2 to C 4 alkyl group, and/or an ether or cyclic ether such as tetrahydrofuran.
  • TEOS tetraethylorthosilicate
  • an ether such as tetrahydrofuran
  • organic alcohol having the formula R′′OH where R′′ is a C 1 -C 12 alkyl group, or a C 1 to C 8 alkyl group, or a C 2 to C 4 alkyl group
  • R′′ is a C 1 -C 12 alkyl group, or a C 1 to C 8 alkyl group, or a C 2 to C 4 alkyl group
  • the metallocene and Ziegler-Natta components may be contacted with the support in any order.
  • the first catalyst component is reacted first with the support as described above, followed by contacting this supported first catalyst component with a second catalyst component.
  • the molar ratio of metal from the second catalyst component to the first catalyst component is a value of from 0.1 to 100 in one embodiment; and from 1 to 50 in another embodiment, and from 2 to 20 in yet another embodiment, and from 3 to 12 in yet another embodiment; and from 4 to 10 in yet another embodiment, and from 4 to 8 in yet another embodiment; wherein a desirable molar ratio of Ti component metal:Zr catalyst component metal is any combination of any upper limit with any lower limit described herein.
  • the polymerization process used to form the polyethylene compositions useful in making the films of the invention preferably comprises injecting a supported catalyst composition into the polymerization reactor.
  • the catalyst components and activator(s) can be combined in any suitable manner with the support, and supported by any suitable means know in the art.
  • the catalyst components are co-supported with at least one activator, preferably an alumoxane.
  • Another activator, preferably an alkylaluminum, is co-injected into the polymerization reactor as a distinct component in another embodiment.
  • the bimetallic catalyst composition preferably comprising a metallocene and Ziegler-Natta catalyst component, is injected into a single reactor, preferably a fluidized bed gas phase reactor, under polymerization conditions suitable for producing a bimodal polyethylene composition as described herein.
  • support refers to any support material, a porous support material in one embodiment, including inorganic or organic support materials.
  • Particularly preferred support materials include silica, alumina, silica-alumina, magnesium chloride, graphite, and mixtures thereof in one embodiment.
  • the support is silica.
  • the support is an inorganic oxide, preferably silica, having an average particle size of less than 50 ⁇ m or less than 35 ⁇ m and a pore volume of from 0.1 to 1 or 2 or 5 cm 3 /g.
  • the support is preferably calcined. Suitable calcining temperatures range from 500° C. to 1500° C. in one embodiment, and from 600° C. to 1200° C. in another embodiment, and from 700° C. to 1000° C. in another embodiment, and from 750° C. to 900° C. in yet another embodiment, and from 800° C. to 900° C. in yet a more particular embodiment, wherein a desirable range comprises any combination of any upper temperature limit with any lower temperature limit. Calcining may take place in the absence of oxygen and moisture by using, for example, an atmosphere of dry nitrogen. Alternatively, calcining may take place in the presence of moisture and air.
  • the support may be contacted with the other components of the catalyst system in any number of ways.
  • the support is contacted with the activator to form an association between the activator and support, or a “bound activator”.
  • the catalyst component may be contacted with the support to form a “bound catalyst component”.
  • the support may be contacted with the activator and catalyst component together, or with each partially in any order.
  • the components may be contacted by any suitable means as in a solution, slurry, or solid form, or some combination thereof, and may be heated when contacted to from 25° C. to 250° C.
  • the bimetallic catalyst composition comprises at least one, preferably one, type of activator.
  • activator is defined to be any compound or combination of compounds, supported or unsupported, which can activate a single-site catalyst compound (e.g., metallocenes, metal amido catalysts, etc.), such as by creating a cationic species from the catalyst component.
  • a single-site catalyst compound e.g., metallocenes, metal amido catalysts, etc.
  • activators include Lewis acids such as cyclic or oligomeric poly(hydrocarbylaluminum oxides).
  • the activator is an alumoxane, and more preferably, an alumoxane supported on an inorganic oxide support material, wherein the support material has been calcined prior to contacting with the alumoxane.
  • alkylaluminum is also added, preferably to the polymerization reactor, as an activator of the Ziegler-Natta component of the bimetallic catalyst in one embodiment.
  • the alkylaluminum activator may be described by the formula AlR ⁇ 3 , wherein R ⁇ is selected from the group consisting of C 1 to C 20 alkyls, C 1 to C 20 alkoxys, halogen (chlorine, fluorine, bromine) C 6 to C 20 aryls, C 7 to C 25 alkylaryls, and C 7 to C 25 arylalkyls.
  • alkylaluminum compounds include trimethylaluminum, triethylaluminum, triisobutylaluminum, tri-n-hexylaluminum, tri-n-octylaluminum and the like.
  • the alkylaluminum is preferably not supported on the support material with the catalyst components and “primary” activator (e.g., alumoxane), but is a separate component added to the reactor(s).
  • the alkylaluminum compound, or mixture of compounds, such as trimethylaluminum or triethylaluminum is feed into the reactor in one embodiment at a rate of from 10 wt. ppm to 500 wt. ppm (weight parts per million alkylaluminum feed rate compared to ethylene feed rate), and from 50 wt. ppm to 400 wt. ppm in a more particular embodiment, and from 60 wt. ppm to 300 wt. ppm in yet a more particular embodiment, and from 80 wt. ppm to 250 wt. ppm in yet a more particular embodiment, and from 75 wt. ppm to 150 wt. ppm in yet another embodiment, wherein a desirable range may comprise any combination of any upper limit with any lower limit.
  • activators may also be useful in making the bimetallic catalyst compositions described herein.
  • Ionizing activators are well known in the art and are described by, for example, Eugene You-Xian Chen & Tobin J. Marks, Cocatalysts for Metal - Catalyzed Olefin Polymerization: Activators, Activation Processes, and Structure - Activity Relationships 100(4) C HEMICAL R EVIEWS 1391-1434 (2000).
  • Illustrative, not limiting examples of ionic ionizing activators include trialkyl substituted ammonium salts such as triethylammonium tetra(phenyl)boron and the like; N,N-dialkyl anilinium salts such as N,N-dimethylanilinium tetra(phenyl)boron and the like; dialkyl ammonium salts such as di-(isopropyl)ammonium tetra(pentafluorophenyl)boron and the like; triaryl carbonium salts (trityl salts) such as triphenylcarbonium tetra(phenyl)boron and the like; and triaryl phosphonium salts such as triphenylphosphonium tetra(phenyl)boron and the like, and their aluminum equivalents.
  • trialkyl substituted ammonium salts such as triethylammonium tetra(phenyl)boron and the like
  • the mole ratio of activator to catalyst component ranges from 2:1 to 100,000:1 in one embodiment, and from 10:1 to 10,000:1 in another embodiment, and from 50:1 to 2,000:1 in yet another embodiment; most preferably, the alumoxane is supported on an inorganic oxide such that, once co-supported with the metallocene, is present in a molar ratio of aluminum(alumoxane):Group 4, 5 or 6 metal (metallocene) from 500:1 to 10:1, and most preferably a ratio of from 200:1 to 50:1.
  • the reactor(s) employing the catalyst system described herein is capable of producing from greater than 500 lbs/hr (230 Kg/hr) in one embodiment, and greater than 1,000 lbs/hr (450 Kg/hr) in another embodiment, and greater than 2,000 lbs/hr (910 Kg/hr) in yet another embodiment, and greater than 10,000 lbs/hr (4500 Kg/hr) in yet another embodiment, greater than 20,000 lbs/hr (9,100 Kg/hr) in yet another embodiment, and up to 500,000 lbs/hr (230,000 Kg/hr) in yet another embodiment.
  • the films of the present invention are extruded and cast or blown from a polyethylene composition formed from a continuous fluidized bed gas phase process, and in particular, utilizing a single fluidized bed reactor in a single stage process.
  • This type of reactor and means for operating the reactor are well known and completely described in, for example, U.S. Pat. Nos. 4,003,712, 4,588,790, 4,302,566, 5,834,571, and 5,352,749.
  • the process can be carried out in a single gas phase reactor as described in U.S. Pat. Nos. 5,352,749 and 5,462,999.
  • These later patents disclose gas phase polymerization processes wherein the polymerization medium is fluidized by the continuous flow of the gaseous monomers and alternately a “condensing agent”.
  • An embodiment of a fluid bed reactor useful in the process of forming the polyethylene of the present invention typically comprises a reaction zone and a so-called velocity reduction zone.
  • the reaction zone comprises a bed of growing polyethylene particles, formed polyethylene particles and a minor amount of catalyst particles fluidized by the continuous flow of the gaseous monomer and optionally diluent to remove heat of polymerization through the reaction zone.
  • some of the re-circulated gases may be cooled and compressed to form liquids that increase the heat removal capacity of the circulating gas stream when readmitted to the reaction zone.
  • a suitable rate of make-up gas flow may be readily determined by simple experiment.
  • Make up of gaseous monomer to the circulating gas stream is at a rate equal to the rate at which particulate polyethylene product and monomer associated therewith is withdrawn from the reactor and the composition of the gas passing through the reactor is adjusted to maintain an essentially steady state gaseous composition within the reaction zone.
  • the gas leaving the reaction zone is passed to the velocity reduction zone where entrained particles are removed. Finer entrained particles and dust may be removed in a cyclone and/or fine filter.
  • the gas is passed through a recycle line and then through a heat exchanger wherein the heat of polymerization is removed, compressed in a compressor and then returned to the reaction zone.
  • control agents e.g., tetrahydrofuran, isopropyl alcohol, molecular oxygen, phenol compounds, ethoxylated amines, etc
  • These agents are known to aid in reduction of electrostatic charge and/or reactor fouling at the expanded region, recycle line, bottom plate, etc.
  • the fluidized bulk density of the polyethylene composition forming in the reactor(s) ranges from 16 to 24 lbs/ft 3 , and from 16.5 to 20 lbs/ft 3 in another embodiment.
  • the reactor(s) useful in making the polyethylene compositions of the present invention preferably operate at a space time yield of from 5 to 20 lb/hr/ft 3 , and more preferably from 6 to 15 lb/hr/ft 3 .
  • the residence time in the reactor(s), preferably one reactor ranges from 1 to 7 hrs, and more preferably from 1.2 to 6 hrs, and even more preferably from 1.3 to 4 hrs.
  • the reactor temperature of the fluidized bed process herein ranges from 70° C. or 75° C. or 80° C. to 90° C. or 95° C. or 100° C. or 110° C., wherein a desirable temperature range comprises any upper temperature limit combined with any lower temperature limit described herein.
  • the reactor temperature is operated at the highest temperature that is feasible, taking into account the sintering temperature of the polyethylene product within the reactor and fouling that may occur in the reactor or recycle line(s).
  • the gas phase reactor pressure wherein gases may comprise hydrogen, ethylene and higher comonomers, and other gases, is between 1 (101 kPa) and 100 atm (10,132 kPa) in one embodiment, and between 5 (506 kPa) and 50 atm (5066 kPa) in another embodiment, and between 10 (1013 kPa) and 40 atm (4050 kPa) in yet another embodiment.
  • the process of the present invention is suitable for the production of homopolymers comprising ethylene derived units, and/or copolymers comprising ethylene derived units and at least one or more other olefin(s) derived units.
  • ethylene is copolymerized with ⁇ -olefins containing from 3 to 12 carbon atoms in one embodiment, and from 4 to 10 carbon atoms in yet another embodiment, and from 4 to 8 carbon atoms in a preferable embodiment.
  • ethylene is copolymerized with 1-butene or 1-hexene, and most preferably, ethylene is copolymerized with 1-butene to form the polyethylene composition useful for the films of the invention.
  • the comonomer may be present at any level that will achieve the desired weight percent incorporation of the comonomer into the finished resin.
  • the comonomer is present with ethylene in the circulating gas stream in a mole ratio range of from 0.005 (comonomer:ethylene) to 0.100, and from 0.0010 to 0.050 in another embodiment, and from 0.0015 to 0.040 in yet another embodiment, and from 0.018 to 0.035 in yet another embodiment.
  • Hydrogen gas may also be added to the polymerization reactor(s) to control the final properties (e.g., I 21 and/or I 2 , bulk density) of the polyethylene composition.
  • the mole ratio of hydrogen to total ethylene monomer (H 2 :C 2 ) in the circulating gas stream is in a range of from 0.001 or 0.002 or 0.003 to 0.014 or 0.016 or 0.018 or 0.024, wherein a desirable range may comprise any combination of any upper mole ratio limit with any lower mole ratio limit described herein.
  • the amount of hydrogen in the reactor at any time may range from 1000 ppm to 20,000 ppm in one embodiment, and from 2000 to 10,000 in another embodiment, and from 3000 to 8,000 in yet another embodiment, and from 4000 to 7000 in yet another embodiment, wherein a desirable range may comprise any upper hydrogen limit with any lower hydrogen limit described herein.
  • the bimetallic catalyst composition may be introduced into the polymerization reactor by any suitable means regardless of the type of polymerization reactor used.
  • the bimetallic catalyst composition is feed to the reactor in a substantially dry state, meaning that the isolated solid form of the catalyst has not been diluted or combined with a diluent prior to entering the reactor.
  • the catalyst composition is combined with a diluent and feed to the reactor; the diluent in one embodiment is an alkane such as a C 4 to C 20 alkane, toluene, xylene, mineral or silicon oil, or combinations thereof, such as described in, for example, U.S. Pat. No. 5,290,745.
  • the bimetallic catalyst composition may be combined with up to 2.5 wt % of a metal-fatty acid compound in one embodiment, such as, for example, an aluminum stearate, based upon the weight of the catalyst system (or its components), such as disclosed in U.S. Pat. No. 6,608,153.
  • a metal-fatty acid compound in one embodiment, such as, for example, an aluminum stearate, based upon the weight of the catalyst system (or its components), such as disclosed in U.S. Pat. No. 6,608,153.
  • Other suitable metals useful in combination with the fatty acid include other Group 2 and Group 5-13 metals.
  • a solution of the metal-fatty acid compound is fed into the reactor.
  • the metal-fatty acid compound is mixed with the catalyst and fed into the reactor separately. These agents may be mixed with the catalyst or may be fed into the reactor in a solution or a slurry with or without the catalyst system or its components.
  • the supported catalyst(s) are combined with the activators and are combined, such as by tumbling and other suitable means, with up to 2.5 wt % (by weight of the catalyst composition) of an antistatic agent, such as an ethoxylated or methoxylated amine, an example of which is Kemamine AS-990 (ICI Specialties, Bloomington Del.).
  • an antistatic agent such as an ethoxylated or methoxylated amine, an example of which is Kemamine AS-990 (ICI Specialties, Bloomington Del.).
  • the polyethylene compositions described herein are multimodal or bimodal in one embodiment, preferably bimodal, and comprise at least one HMW polyethylene and at least one LMW polyethylene in a particular embodiment.
  • the term “bimodal,” when used to describe the polyethylene composition means “bimodal molecular weight distribution,” which term is understood as having the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents.
  • a single polyethylene composition that includes polyolefins with at least one identifiable high molecular weight distribution and polyolefins with at least one identifiable low molecular weight distribution is considered to be a “bimodal” polyolefin, as that term is used herein.
  • Those high and low molecular weight polymers may be identified by deconvolution techniques known in the art to discern the two polymers from a broad or shouldered GPC curve of the bimodal polyolefins of the invention, and in another embodiment, the GPC curve of the bimodal polymers of the invention may display distinct peaks with a trough as shown in the examples in FIGS. 3-5 .
  • the polyethylene compositions of the invention may be characterized by a combination of features.
  • the polyethylene composition is a poly(ethylene-co-1-butene) or a poly(ethylene-co-1-hexene), preferably poly(ethylene-co-1-butene), the comonomer present from 0.1 to 5 mole percent of the polymer composition, primarily on the LMW polyethylene of the polyethylene composition.
  • the polyethylene compositions of the invention have a density in the range of 0.940 g/cm 3 to 0.970 g/cm 3 in one embodiment, in the range of from 0.942 g/cm 3 to 0.968 g/cm 3 in another embodiment, and in the range of from 0.943 g/cm 3 to 0.965 g/cm 3 in yet another embodiment, and in the range of from 0.944 g/cm 3 to 0.962 g/cm 3 in yet another embodiment, wherein a desirable density range of the polyethylene compositions of the invention comprise any combination of any upper density limit with any lower density limit described herein.
  • the polyethylene compositions of the present invention can be characterized by their molecular weight characteristics such as measured by GPC, described herein.
  • the polyethylene compositions of the invention have an number average molecular weight (Mn) value of from 2,000 to 70,000 in one embodiment, and from 10,000 to 50,000 in another embodiment, and an weight average molecular weight (Mw) of from 50,000 to 2,000,000 in one embodiment, and from 70,000 to 1,000,000 in another embodiment, and from 80,000 to 800,000 in yet another embodiment.
  • the bimodal polyolefins of the present invention also have a z-average molecular weight (Mz) value ranging from greater than 200,000 in one embodiment, and from greater than 800,000 in another embodiment, and from greater than 900,000 in one embodiment, and from greater than 1,000,000 in one embodiment, and greater than 1,100,000 in another embodiment, and from greater than 1,200,000 in yet another embodiment, and from less than 1,500,000 in yet another embodiment; wherein a desirable range of Mn, Mw or Mz comprises any combination of any upper limit with any lower limit as described herein.
  • Mz z-average molecular weight
  • the polyethylene compositions of the invention have a molecular weight distribution, a weight average molecular weight to number average molecular weight (M w /M n ), or “Polydispersity index”, of from greater than 30 or 40 in a preferable embodiment; and a range of from 30 to 250 in one embodiment, and from 35 to 220 in another embodiment, and from 40 to 200 in yet another embodiment, wherein a desirable embodiment comprises any combination of any upper limit with any lower limit described herein.
  • M w /M n weight average molecular weight to number average molecular weight
  • the polyethylene compositions also have a “z-average” molecular weight distribution (M z /M w ) of from 2 to 20 in one embodiment, from 3 to 20 in another embodiment, and from 4 to 10 in another embodiment, and from 5 to 8 in yet another embodiment, and from 3 to 10 in yet another embodiment, wherein a desirable range may comprise any combination of any upper limit with any lower limit.
  • M z /M w z-average molecular weight distribution
  • the polyethylene composition of the present invention possess a melt index (MI, or I 2 as measured by ASTM-D-1238-E 190° C./2.16 kg) in the range from 0.01 dg/min to 50 dg/min in one embodiment, and from 0.02 dg/min to 10 dg/min in another embodiment, and from 0.03 dg/min to 2 dg/min in yet another embodiment, wherein a desirable range may comprise any upper limit with any lower limit described herein.
  • MI melt index
  • the polyethylene compositions of the invention possess a flow index (FI or I 21 as measured by ASTM-D-1238-F, 190° C./21.6 kg) ranging from 4 to 20 dg/min in one embodiment, and from 4 to 18 dg/min in another embodiment, and from 5 to 16 dg/min in yet another embodiment, and from 6 to 14 dg/min in yet another embodiment; and a range of from 6 to 12 dg/min in yet another embodiment, wherein a desirable I 21 range may comprise any upper limit with any lower limit described herein.
  • FI or I 21 as measured by ASTM-D-1238-F, 190° C./21.6 kg
  • the polyethylene compositions in certain embodiments have a melt index ratio (I 21 /I 2 ) of from 80 to 400, and from 90 to 300 in another embodiment, and from 100 to 250 in yet another embodiment, and from 120 to 220 in yet another embodiment, wherein a desirable I 21 /I 2 range may comprise any combination of any upper limit with any lower limit described herein.
  • the polyethylene compositions comprise greater than 50 wt % by weight of the total composition of HMW polyethylene, and greater than 55 wt % in another embodiment, and in another embodiment, between 50 and 80 wt %, and between 55 and 75 wt % in yet another embodiment, and between 55 and 70 wt % in yet another embodiment, the weight percentages determined from GPC measurements.
  • the polyethylene compositions of the invention possess a dynamic viscosity ⁇ at 200° C. and 0.1/sec of from 100 kPoise to 3000 kPoise in one embodiment, 300 kPoise to 1400 kPoise in another embodiment, from 350 kPoise to 1000 kPoise in another embodiment, and from 400 kPoise to 800 kPoise in another embodiment, and from 500 kPoise to 700 kPoise in yet another embodiment.
  • Dynamic viscosity in the examples herein was measured according to ASTM D4440-95 using a nitrogen atmosphere, 1.5 mm die gap and 25 mm parallel plates at 200° C. and 0.1/sec.
  • the polyethylene composition useful for making the films has an elasticity of greater than 0.60, and greater than 0.61 in another embodiment, and greater than 0.62 in yet another embodiment, and greater than 0.63 in yet another embodiment.
  • the individual components of the polyethylene composition may also be described by certain embodiments, and in one embodiment, the polyethylene composition comprises one HMW polyethylene and one LMW polyethylene; and in another embodiment, the polyethylene composition consists essentially of one HMW polyethylene and one LMW polyethylene.
  • the molecular weight distribution (Mw/Mn) of the HMW polyethylene ranges from 3 to 24, and ranges from 4 to 24 in another embodiment, and from 6 to 18 in another embodiment, and from 7 to 16 in another embodiment, and from 8 to 14 in yet another embodiment, wherein a desirable range comprises any combination of any upper limit with any lower limit described herein.
  • the HMW polyethylene has a weight average molecular weight ranging from greater than 50,000 amu in one embodiment, and ranging from 50,000 to 1,000,000 amu in one embodiment, and from 80,000 to 900,000 amu in another embodiment, and from 100,000 to 800,000 amu in another embodiment, and from 250,000 to 700,000 amu in another embodiment, wherein a desirable range comprises any combination of any upper limit with any lower limit described herein.
  • the weight fraction of the HMW polyethylene in the polyethylene composition ranges may be at any desirable level depending on the properties that are desired in the polyethylene composition; in one embodiment the HMW polyethylene weight fraction ranges from 0.3 to 0.7; and from 0.4 to 0.6 in another particular embodiment, and ranges from 0.5 and 0.6 in yet another particular embodiment.
  • the molecular weight distribution (Mw/Mn) of the LMW polyethylene ranges from 1.8 to 6, and from 2 to 5 in another embodiment, and from 2.5 to 4 in yet another embodiment, wherein a desirable range comprises any combination of any upper limit with any lower limit described herein.
  • the LMW polyethylene has a weight average molecular weight ranging from 2,000 to 50,000 amu in one embodiment, and from 3,000 to 40,000 in another embodiment, and from 4,000 to 30,000 amu in yet another embodiment wherein a desirable range of LMW polyethylene in the polyethylene composition comprises any combination of any upper limit with any lower limit described herein.
  • the weight average molecular weight of the LMW polyethylene is less than 50,000 amu, and less than 40,000 amu in another embodiment, and less than 30,000 amu in yet another embodiment, and less than 20,000 amu in yet another embodiment, and less than 15,000 amu in yet another embodiment, and less than 13,000 amu in yet another embodiment.
  • the LMW polyethylene has an I 2 value of from 0.1 to 10,000 dg/min in one embodiment, and from 1 to 5,000 dg/min in another embodiment, and from 100 to 3,000 dg/min in yet another embodiment; and an I 21 of from 2.0 to 300,000 dg/min in one embodiment, from 20 to 150,000 dg/min in another embodiment, and from 30 to 15,000 dg/min in yet another embodiment; wherein for the I 2 and I 21 values, a desirable range comprises any combination of any upper limit with any lower limit described herein.
  • the I 2 and I 21 of the LMW polyethylene may be determined by any technique known in the art; and in one embodiment is determined by deconvolution of the GPC curve.
  • Granules of polyethylene material are formed from the processes described herein in making the polyethylene composition.
  • one or more additives may be blended with the polyethylene composition.
  • One method of blending the additives with the polyolefin is to contact the components in a tumbler or other physical blending means, the polyolefin being in the form of reactor granules. This can then be followed, if desired, by melt blending in an extruder.
  • Another method of blending the components is to melt blend the polyolefin pellets with the additives directly in an extruder, Brabender or any other melt blending means, preferably an extruder.
  • suitable extruders include those made by Farrel and Kobe. While not expected to influence the measured properties of the polyethylene compositions described herein, the density, rheological and other properties of the polyethylene compositions described in the Examples are measured after blending additives with the compositions.
  • Non-limiting examples of additives include processing aids such as fluoroelastomers, polyethylene glycols and polycaprolactones, antioxidants, nucleating agents, acid scavengers, plasticizers, stabilizers, anticorrosion agents, blowing agents, other ultraviolet light absorbers such as chain-breaking antioxidants, etc., quenchers, antistatic agents, slip agents, pigments, dyes and fillers and cure agents such as peroxide.
  • processing aids such as fluoroelastomers, polyethylene glycols and polycaprolactones, antioxidants, nucleating agents, acid scavengers, plasticizers, stabilizers, anticorrosion agents, blowing agents, other ultraviolet light absorbers such as chain-breaking antioxidants, etc., quenchers, antistatic agents, slip agents, pigments, dyes and fillers and cure agents such as peroxide.
  • antioxidants and stabilizers such as organic phosphites, hindered amines, and phenolic antioxidants may be present in the polyolefin compositions of the invention from 0.001 to 2 wt % in one embodiment, and from 0.01 to 1 wt % in another embodiment, and from 0.05 to 0.8 wt % in yet another embodiment; described another way, from 1 to 5000 ppm by weight of the total polymer composition, and from 100 to 3000 ppm in a more particular embodiment.
  • Non-limiting examples of organic phosphites that are suitable are tris(2,4-di-tert-butylphenyl)phosphite (IRGAFOS 168) and di(2,4-di-tert-butylphenyl)pentaerithritol diphosphite (ULTRANOX 626).
  • Non-limiting examples of hindered amines include poly[2-N,N′-di(2,2,6,6-tetramethyl-4-piperidinyl)-hexanediamine-4-(1-amino-1,1,3,3-tetramethylbutane)symtriazine] (CHIMASORB 944); bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate (TINUVIN 770).
  • Non-limiting examples of phenolic antioxidants include pentaerythrityl tetrakis(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (IRGANOX 1010); 1,3,5-Tri(3,5-di-tert-butyl-4-hydroxybenzyl-isocyanurate (IRGANOX 3114); tris(nonylphenyl)phosphite (TNPP); and Octadecyl-3,5-Di-(tert)-butyl-4-hydroxyhydrocinnamate (IRGANOX 1076); other additives include those such as zinc stearate and zinc oleate.
  • Fillers may be present from 0.01 to 5 wt % in one embodiment, and from 0.1 to 2 wt % of the composition in another embodiment, and from 0.2 to 1 wt % in yet another embodiment and most preferably, between 0.02 and 0.8 wt %.
  • Desirable fillers include but not limited to titanium dioxide, silicon carbide, silica (and other oxides of silica, precipitated or not), antimony oxide, lead carbonate, zinc white, lithopone, zircon, corundum, spinel, apatite, Barytes powder, barium sulfate, magnesiter, carbon black, acetylene black, dolomite, calcium carbonate, talc and hydrotalcite compounds of the ions Mg, Ca, or Zn with Al, Cr or Fe and CO 3 and/or HPO 4 , hydrated or not; quartz powder, hydrochloric magnesium carbonate, glass fibers, clays, alumina, and other metal oxides and carbonates, metal hydroxides, chrome, phosphorous and brominated flame retardants, antimony trioxide, silica, silicone, and blends thereof. These fillers may particularly include any other fillers and porous fillers and supports known in the art.
  • fillers, antioxidants and other such additives are preferably present to less than 2 wt % in the polyethylene compositions of the present invention, preferably less than 1 wt %, and most preferably to less than 0.8 wt % by weight of the total composition.
  • an oxidizing agent is also added during the pelletizing step as a reactive component with the polyethylene composition.
  • the compositions are extruded with an oxidizing agent, preferably oxygen, as disclosed in WO 03/047839.
  • an oxidizing agent preferably oxygen, as disclosed in WO 03/047839.
  • from 0.01 or 0.1 or 1 to 14 or 16 SCFM (standard cubic feet per minute) of oxygen is added to the polyethylene composition during extrusion to form the film, the exact amount depending upon the type of extruder used and other conditions.
  • an inert gas such as nitrogen is introduced to the extruding polymer composition in one embodiment.
  • enough oxygen is added to the extruder to raise the I 21 /I 2 value of the polyethylene composition from the reactor(s) by from 1 to 40%, and from 5 to 25% in another embodiment.
  • the pellets produced therefrom are then used to extrude the films of the invention in a separate line, for example, and Alpine line.
  • the resultant pelletized polyethylene compositions, with or without additives, are processed by any suitable means for forming films: film blowing or casting and all methods of film formation to achieve, for example, uniaxial or biaxial orientation such as described in P LASTICS P ROCESSING (Radian Corporation, Noyes Data Corp. 1986).
  • the polyethylene compositions of the present invention are formed into films such as described in the F ILM E XTRUSION M ANUAL , P ROCESS , M ATERIALS , P ROPERTIES (TAPPI, 1992).
  • the films of the present invention are blown films, the process for which is described generally in F ILM E XTRUSION M ANUAL , P ROCESS , M ATERIALS , P ROPERTIES pp. 16-29, for example.
  • any extruder suitable for extrusion of a HDPE (density greater than 0.940 g/cm 3 ) operating under any desirable conditions for the polyethylene compositions described herein can be used to produce the films of the present invention.
  • Such extruders are known to those skilled in the art.
  • Such extruders include those having screw diameters ranging from 30 to 150 mm in one embodiment, and from 35 to 120 mm in another embodiment, and having an output of from 100 to 1,500 lbs/hr in one embodiment, and from 200 to 1,000 lbs/hr in another embodiment.
  • a grooved feed extruder is used.
  • the extruder may possess a L/D ratio of from 80:1 to 2:1 in one embodiment, and from 60:1 to 6:1 in another embodiment, and from 40:1 to 12:1 in yet another embodiment, and from 30:1 to 16:1 in yet another embodiment.
  • a mono or multi-layer die can be used.
  • a 50 to 200 mm monolayer die is used, and a 90 to 160 mm monolayer die in another embodiment, and a 100 to 140 mm monolayer die in yet another embodiment, the die having a nominal die gap ranging from 0.6 to 3 mm in one embodiment, and from 0.8 to 2 mm in another embodiment, and from 1 to 1.8 mm in yet another embodiment, wherein a desirable die can be described by any combination of any embodiment described herein.
  • the advantageous specific throughputs claimed herein are maintained in a 50 mm grooved feed extruder with an L/D of 21:1 in a particular embodiment.
  • the temperature across the zones of the extruder, neck and adapter of the extruder ranges from 150° C. to 230° C. in one embodiment, and from 160° C. to 210° C. in another embodiment, and from 170° C. to 190° C. in yet another embodiment.
  • the temperature across the die ranges from 160° C. to 250° C. in one embodiment, and from 170° C. to 230° C. in another embodiment, and from 180° C. to 210° C. in yet another embodiment.
  • films of the present invention can be described alternately by any of the embodiments disclosed herein, or a combination of any of the embodiments described herein.
  • Embodiments of the invention while not meant to be limiting by, may be better understood by reference to the following examples.
  • the following examples relate to gas phase polymerization procedures carried out in a fluidized bed reactor capable of producing from greater than 500 lbs/hr (230 Kg/hr) at a production rate of from 8 to 40 T/hr or more, utilizing ethylene and 1-butene comonomer, resulting in production of the polyethylene composition.
  • the tables identify various samples of resin and films made from those samples, along with the reported reaction conditions during the collection of the samples (“examples”). Various properties of the resulting resin products and film products are also identified. Examples 1 and 2 were extruded in the absence of oxygen (“non-tailored”) as described below, while the Examples 3-9 were extruded in the presence of oxygen (“oxygen tailored”) as per WO 03/047839, herein incorporated by reference. The comparative examples were made into films as received.
  • the fluidized bed of the reactor was made up of polyethylene granules.
  • the reactor is passivated with an alkylaluminum, preferably trimethylaluminum.
  • the gaseous feed streams of ethylene and hydrogen were introduced before the reactor bed into a recycle gas line.
  • the injections were downstream of the recycle line heat exchanger and compressor.
  • Liquid 1-butene comonomer was introduced before the reactor bed.
  • the control agent typically isopropyl alcohol
  • if any that influenced resin split and helped control fouling, especially bottom plate fouling, was added before the reactor bed into a recycle gas line in gaseous or liquid form.
  • the individual flows of ethylene, hydrogen and 1-butene comonomer were controlled to maintain target reactor conditions, as identified in each example.
  • the concentrations of gases were measured by an on-line chromatograph.
  • the examples 1 and 2 were samples taken from a 3-4 day polymerization run on a single gas phase fluidized bed reactor having a diameter of 8 feet and a bed height (from distributor “bottom” plate to start of expanded section) of 38 feet.
  • the examples 3-9 were samples taken from a different 3-4 day polymerization run on a single gas phase fluidized bed reactor having a diameter of 11.3 feet and a bed height (from distributor “bottom” plate to start of expanded section) of 44.6 feet.
  • supported bimetallic catalyst was injected directly into the fluidized bed using purified nitrogen. Catalyst injection rates were adjusted to maintain approximately constant production rate.
  • the catalyst used was made with silica dehydrated at 875° C., and metallocene compound Cp 2 MX 2 wherein Cp is an n-butyl-substituted cyclopentadienyl ring, M is Zirconium; and X is fluoride.
  • the titanium source for the Ziegler-Natta component was TiCl 4 .
  • each polymerization run for the inventive examples utilized a target reactor temperature (“Bed Temperature”), namely, a reactor temperature of about 95° C.
  • reactor temperature was maintained at an approximately constant level by adjusting up or down the temperature of the recycle gas to accommodate any changes in the rate of heat generation due to the polymerization.
  • the example polymer compositions were extruded in a 4 inch Farrel (or Kobe) Continuous Mixer (4UMSD) at rate of 500 lbs/hr, specific energy input of 0.125 HP-Hr/lb to form pellets.
  • An additive package was also added such that the Examples 1-9 polymer compositions comprising 800 ppm (IRGANOX 1010, Pentaerythrityltetrakis-3-(3,5-di-tert-butyl-4-hydroxyphenyl)-Propionate), 200 ppm (IRGAFOS 168, Tris(2,4-di-tert-butyl-phenyl)phosphite) and 1500 ppm zinc stearate.
  • the examples 1 and 2 were extruded in a nitrogen atmosphere (0% Oxygen); examples 3-9 were extruded in the presence of an amount of oxygen as disclosed in WO 03/047839.
  • the polymer composition properties are described in the tables.
  • the examples 1 and 2 were extruded blown film line under the conditions listed in Table 2; the extruder screw being a 50 mm 21 d screw with a “LLDPE” feed section (Alpine part no. 171764).
  • the melt temperature T m was measured by an immersion thermocouple at the adapter section, near the exit of the extruder. Chilled air was applied to the outside of the bubble for cooling purposes.
  • the cast film system includes dual stainless steel chrome plated and polished chill rolls, a machined precision air knife, rubber nip rolls that pull the film through the gel counter, and a torque driven wind up roll.
  • the nip rolls are driven separately from the chill rolls and are controlled by speed or tension.
  • a circulation cooling/heating system for the chill rolls was also included, and utilizes ethylene glycol.
  • Steel SS rails, film break sensors, and other items were included.
  • the example 3-9 and C1 films that were measured were from 1 mil (25 ⁇ m) in thickness, the comparative films C2, C3 and C5 were 2 mil (50 ⁇ m) films.
  • the gel counter consists of a digital 2048 pixel line camera, a halogen based line lighting system, an image processing computer, and Windows NT4 software.
  • the camera/light system was mounted on the cast film system between the chill roll and nip rolls, and was set up for a 50 micron resolution on film. This means that the smallest defect that could be seen was 50 microns by 50 microns in size.
  • the pellet samples were run with constant extruder temperatures (180° C. for the feed zone, 190° C. for all remaining zones), and constant chill roll temperature of 40° C.
  • the extruder and chill roll speeds were varied slightly between samples to provide an optimum film for each sample. With more experimentation, one set of operating conditions might be found that are satisfactory for all samples.
  • the gel counter was set up with 10 different size classes beginning at 50-100 microns and increasing at 100 micron intervals, 4 different shape classes beginning with a perfect circular shape and increasing to more oblong shapes, and two detection levels (one for gels and one for black specks).
  • the gel detection level or sensitivity used was 35 on a 0 to 100 scale.
  • the extruder was purged with the first sample (typically about 20 minutes) or until it was apparent that the test conditions were at steady state, or “equilibrium”. This was done by looking at a trend line chart of gel count number on the “y” axis, and time on the “x” axis. Tests were then run on 3 square meters of film per test, as the film moved by the camera. Three tests were run in succession on the sample, in order to determine test repeatability. At the end of each 3 square meter test, tabular results were printed. After the purge time, a set of 3 successive 3 square meter tests was performed for the second sample, and results printed.
  • the gel counts reported in the tables were normalized to gauge. Each sample was tested three times. The data provided from the test was used to calculate the sum of all gels 200 microns in size or smaller. The three runs from each sample were averaged, then that average divided by the gauge in mils. The gel count results are normalized as the number of gels less than 200 ⁇ m in size contained in a 3 m 2 film sample of 1 mil thickness, or a volume of 7.62 ⁇ 10 ⁇ 5 m 3 .
  • Comparative Example 1 (“C1”) is a single reactor (gas phase) produced bimodal polyethylene having the properties listed in Tables 2 and 4. It was made using a bimetallic catalyst system similar to the catalyst composition described above for the inventive examples.
  • a granular sample of the C1 was obtained and blended with 1500 ppm Tetrakis[methylene(3,5-di-t-butyl-4-hydroxyhydrocinnamate)]methane, commonly known as IRGANOX 1010, 1500 ppm Tris(2,4-di-t-butylphenyl)phosphite (commonly known as IRGAFOS 168 and 1500 ppm zinc stearate.
  • the blended material was melt homogenized under a nitrogen blanket on a laboratory scale Brabender single screw extruder. The FI, MFR and density of the melt homogenized material was measured and is reported in Table 2.
  • Comparative Example 2 (“C2”) is a Dow UNIPOLTM II 2100 bimodal poly(ethylene-co-1-butene) produced in a two-staged dual reactor gas phase process using a Ziegler-Natta type catalyst.
  • Comparative Example 3 (“C3”) is a Mitsui HD7960 bimodal poly(ethylene-co-1-butene) produced in a two-staged slurry process, available from ExxonMobil Chemical Co.
  • Comparative Example 4 (“C4”) is a Mitsui HD7755 bimodal poly(ethylene-co-1-butene) produced in a two-staged slurry process, available from ExxonMobil Chemical Co.
  • Comparative Example 5 (“C5”) is a AlathonTM L5005 bimodal poly(ethylene-co-1-butene) produced in a two-staged process available from Equistar Chemicals. TABLE 1 Process Parameters in forming the polyethylene compositions corresponding to examples 1 and 2, and polymer characteristics 1 2 Process Parameter amount of polymer lbs 190,000 230,000 collected in 24 hr ( ⁇ 10%) H 2 /C 2 Gas Ratio Mol/mol 0.011 0.011 C 4 /C 2 Gas Ratio Mol/mol 0.026 0.024 C 4 /C 2 Flow Ratio Kg/kg 0.0147 0.0152 Ethylene partial pressure Bara 11.3 13.8 Water/C 2 Flow Ratio wt ppm 20.8 20.1 Ti Activity Kg PE/kg 8166 — catalyst TMA in resin wt ppm 113 113 Reactor temperature ° C.
  • the examples 1 and 2 produced in a single gas phase reactor using a bimetallic catalyst as described, produced polymer compositions having the unexpected benefit of improved processability over prior single reactor bimodal resins and a dual-reactor produced bimodal resin commonly known.
  • the lower power, as also represented in FIGS. 1 and 2 represent a dramatic improvement in film production, as the inventive polymer compositions can be more easily processed, thus improving its commercial value. This is especially so given that the I 21 values for examples 1 and 2 are lower than that for both comparative examples, thus the expectation that the flow through the die to form the film would take more power, not less.
  • the melt temperature of the inventive examples 1 and 2 is significantly lower when compared to the comparative examples, thus also an improvement in processability.
  • a melt temperature of less than 180° C., and less than 179° C. in a particular embodiment, is found in the inventive examples, while still maintaining a high specific die rate of at least 10 lbs polymer/hr/inch of die circumference and high specific throughput.
  • the specific throughputs could be at least 1.90 lbs polyethylene/hr/rpm (0.863 kg/hr/rpm) higher at similar melt temperatures.
  • Reactor conditions for runs to produce the polyethylene compositions corresponding to film examples 3-9 are in Table 3 below.
  • the polyethylene composition properties of those corresponding examples are found in Table 4.
  • Film extrusion conditions for examples 3-9, and for determination of the relationship T m ⁇ 235 ⁇ 3.3 (I 21 ) and its specific embodiments, are as follows: an Alpine extruder line having a 50 mm grooved feed extruder, an L/D ratio of 21:1, a temperature profile of 180° C. flat across the extruder, and 190° C.
  • the examples 3-9 exhibited no detectable odor, whereas the C1 sample has some odor upon extrusion.
  • the examples 3-9 although oxygen tailored and thus exhibiting, on average, larger I 21 values and larger I 2 values, still show the improvements of the invention, as these resins are also more easily processed relative to the prior art resins. TABLE 3 Polymerization conditions for Examples 3 through 9 Parameter Units 3 4 5 6 7 8 9 Amt.
  • the advantages of the films of the present invention can be seen from the data.
  • the motor loads expressed as a percentage of the maximum motor load allowable for the equipment used, are significantly lower—all less than 77 to 78%—for the examples 3 through 9, while that for each comparative was typically higher; further, the melt temperatures for the inventive examples were significantly lower than for most of the inventive examples.
  • examples 3-9 follow the relationship T m ⁇ 235 ⁇ 3.3 (I 21 ), wherein the polyethylene composition is extruded at a specific throughput of from 1 to 1.5 lbs/hr/inch, as represented graphically at FIG. 6 .
  • T m ⁇ T m x ⁇ 3.3 (I 21 ) is also followed when comparing the examples 1 and 2, and the examples 3-9, each set having been extruded under differing conditions and using a different extruder screws.
  • the present invention is shown to offer significant improvement over other prior art bimodal resins having a I 21 value of less than 20 and density with the range of 0.930 and 0.970 g/cm 3 , this improvement quite significant when taking into account the large commercial quantities of resin being processed in commercial-scale extruders.

Abstract

A film comprising a polyethylene composition, the polyethylene composition in one embodiment comprising a high molecular weight component having a weight average molecular weight of greater than 50,000 amu and a low molecular weight component having a weight average molecular weight of less than 50,000 amu; the polyethylene composition possessing a density of between 0.940 and 0.970 g/cm3, and an I21 value of less than 20 dg/min; characterized in that the polyethylene composition extrudes at an advantageously high specific throughput at an advantageously low melt temperature, and wherein the film has a gel count of less than 100.

Description

    CROSS-REFERENCE TO RELATED APPLICATION
  • The present application is a continuation of and claims priority to U.S. Ser. No. 10/781,404, filed Feb. 18, 2004, which claims priority to provisional U.S. Ser. No. 60/527,480, filed Dec. 5, 2003, herein incorporated by reference.
  • FIELD OF THE INVENTION
  • The present invention relates to polyethylene films, and more particularly, relates to bimodal polyethylene compositions useful in films having a low level of film impurities and enhanced processability.
  • BACKGROUND OF THE INVENTION
  • High density bimodal polyethylene compositions, and in particular, high density “bimodal” or “multimodal” polyethylenes (“bHDPE”), are known to be useful in making films suitable for a variety of commercial products such as films, pipes, blow molding, etc. However, the costs of producing such compositions is a disadvantage—being relatively high—as most bHDPEs are produced in two stages or more, and/or in two or more staged reactors such as the processes of Dow, Basell, Borealis and Mitsui. Such commercial polymerization systems are reviewed in, for example, 2 METALLOCENE-BASED POLYOLEFINS 366-378 (John Scheirs & W. Kaminsky, eds. John Wiley & Sons, Ltd. 2000).
  • Further, the processing of bHDPEs can present further commercial problems. For example, it is known that film cooling, upon extrusion of the polyethylene, is a limiting factor in film production, especially for extrusion of high density polyethylene, such as described in FILM EXTRUSION MANUAL, PROCESS, MATERIALS, PROPERTIES, pp. 497 (TAPPI, 1992). One solution to this problem is to operate at a desirably low melt temperature. However, given the bimodal nature of these resins, melting may be uneven, and/or relatively high melt temperatures must be maintained for the given resin. To compensate, high back pressures can be maintained, but this can lead to other problems, and consumes more energy. What would be desirable is a bHDPE that can be extruded at a rapid rate at a relatively low melt temperature, using lower extruder motor loads, while maintaining high film quality.
  • As a further advantage, it would be desirable to use a low cost process to produce bHDPE. Single reactor systems may offer such a cost advantage. While single reactor systems have been described as capable of producing bimodal polyethylenes for film applications, such as described by H-T. Liu et al. in 195 MACROMOL. SYMP. 309-316 (July, 2003), those films must still match the quality and processability of current dual-reactor derived polyethylene films for commercial viability. The present invention in one aspect is directed towards such a film, as the inventors have found that a certain balance of polymer properties can meet these commercial needs to produce polyethylene films suitable for cast, blown and other film products; and further, that it is possible to achieve these ends using single-reactor produced polyethylene compositions.
  • SUMMARY OF THE INVENTION
  • In one aspect, the present invention provides a film comprising a polyethylene composition, preferably a bimodal polyethylene, possessing a density of between 0.940 and 0.970 g/cm3, and an I21 value of less than 20 dg/min; characterized in that the polyethylene composition extrudes at a melt temperature, Tm, that satisfies the following relationship: Tm≦235−3.3 (I21); wherein the polyethylene composition is extruded at a specific throughput of from 1 (0.454 kg/hr/rpm) to 1.5 lbs/hr/inch (0.681 kg/hr/rpm), and wherein the film has a gel count of less than 100.
  • In another aspect, the present invention provides a film comprising a polyethylene composition, preferably a bimodal polyethylene, the polyethylene composition comprising a high molecular weight component having a weight average molecular weight of greater than 50,000 amu and a low molecular weight component having a weight average molecular weight of less than 40,000 amu or less than 20,000 amu or less than 15,000 amu or less than 12,000 amu; the polyethylene composition possessing a density of between 0.940 and 0.970 g/cm3, and an I21 value of less than 20 dg/min and a Mw/Mn value of from greater than 30 or 35 or 40; characterized in that the film has a gel count of less than 100.
  • In yet another aspect of the invention, the polyethylene compositions useful for the films of the invention are produced in a single reactor, preferably a single continuous gas phase reactor.
  • Various aspects of the present invention can be described by any one, or combination, of embodiments describing the polymer composition, extrusion properties of the polymer composition, and film, those embodiments described in more detail herein.
  • BRIEF DESCRIPTION OF THE FIGURES
  • FIGS. 1 and 2 are graphical representations of melt index (I21) values of the inventive examples 1 and 2 (♦) and comparative examples (Δ, □) versus motor loads and pressures upon extrusion to form a film of 0.5 mil gauge, extruded at a specific throughput of from 1.84 to 1.90 lbs/hr/rpm;
  • FIGS. 3, 4 and 5 are graphical representations of data obtained from GPC comparing the molecular weight profile of the comparative example 1 (—) with each of inventive examples 3, 4 and 5 (- - - - - ); and
  • FIGS. 6 and 7 are graphical representations of melt index (I21) values of the inventive examples 3 and 5 through 9 (♦) and comparative examples (numbered open circles) versus motor loads and pressures upon extrusion to form a film of 0.5 mil gauge, extruded at a specific throughput of from 1.16 to 1.20 lbs/hr/rpm.
  • DETAILED DESCRIPTION OF THE INVENTION
  • The present invention is to a film comprising a polyethylene composition, the polyethylene composition in one embodiment comprising a high molecular weight component and a low molecular weight component and, in a particular embodiment, displaying a multimodal or bimodal GPC profile. The polyethylene composition has improved processing properties as exhibited by a decreased extruder motor load (or power consumption) relative to other polyethylene resins of similar density and flow index (I21). Further characteristic of the invention is the high specific throughput capabilities at advantageously low melt temperatures. The films described herein possess these improved processing properties while maintaining a high film quality, as exemplified by low gel content, while maintaining the strength, flexibility and impact strength comparable to polyethylenes of similar density and I21.
  • As used herein, the term “film” or “films” includes skins, sheets, or membranes of a thickness of from less than 1000 μm, more preferably from less than 500 μm thickness, and even more preferably less than 200 μm, and most preferably from less than 100 μm, and includes films fabricated by any process known in the art such as by casting or blowing techniques—oriented or not—from an extruded or calendered, preferably extruded, polyethylene as defined herein, and the use of which can include any number of functions such as wrapping, protecting, packaging, bagging, coating, co-extrusion with other materials; and further, may have any commercially desirable dimensions of width, length, etc. The films of the present invention are not limited to transparent films, and may be opaque or translucent or transparent, preferably transparent, and have other properties as defined herein. The films of the present invention may be co-extruded with or otherwise secured to other sheets/structures, etc. to form structures of thickness greater than 1000 μm.
  • The benefits inherent in the films of the invention—the requirement of lower motor loads in extruding the polymer compositions to form the films, and concomitant with that, the lower melt temperatures achievable, both while maintaining a commercially acceptable specific throughput and high film quality as measured by the low gel levels and/or high FAR values—can be described by any number embodiments such as described herein.
  • One aspect of the invention is to a film comprising a polyethylene composition possessing a density of between 0.940 and 0.970 g/cm3, and an I21 value of from 4 to 20 dg/min; characterized in that the polyethylene composition extrudes at a melt temperature, Tm, that satisfies the following relationship (I):
    T m≦235−3.3(I 21)  (I)
    wherein the polyethylene composition is extruded at a specific throughput of from 1 (0.454 kg/hr/rpm) to 1.5 lbs/hr/rpm (0.681 kg/hr/rpm), and wherein the film has a gel count of less than 100. The value “I21” is understood to be multiplied by the number “3.3”. In another embodiment of (I), the melt temperature is described by the relationship Tm≦240−3.3 (I21); and in another embodiment, Tm≦240−3.5 (I21); and in yet another embodiment, Tm≦235−3.5 (I21). The melt temperature is the temperature at the downstream end of the mixing zone of the extruder used in processing the polyethylene composition to form the films of the invention. In this aspect of the invention, the melt temperatures are determined from an extrusion line suitable to form the film as described herein.
  • In one embodiment, the polyethylene composition can be described as extruding at a specific throughput of from 1.00 lbs polyethylene/hr/rpm (0.454 kg/hr/rpm) to 1.45 lbs polyethylene/hr/rpm (0.648 kg/hr/rpm) at a melt temperature Tm satisfying the equation Tm≦235−3.3 (I21).
  • In another embodiment, the polyethylene composition extrudes at a specific throughput of from 1.00 lbs polyethylene/hr/rpm (0.454 kg/hr/rpm) to 1.40 lbs polyethylene/hr/rpm (0.636 kg/hr/rpm) at a melt temperature Tm satisfying the equation Tm≦235−3.3 (I21).
  • In yet another embodiment, the polyethylene composition extrudes at a specific throughput of from 1.00 lbs polyethylene/hr/rpm (0.454 kg/hr/rpm) to 1.30 lbs polyethylene/hr/rpm (0.590 kg/hr/rpm) at a melt temperature Tm satisfying the equation Tm≦235−3.3 (I21). In another embodiment, the lower specific throughput limit is 1.10 lbs polyethylene/hr/rpm (0.499 kg/hr/rpm).
  • Examples of desirable melt temperatures Tm for the polyethylene compositions of the present invention are values less than 206° C. or 204° C. or 202° C. or 200° C. or 198° C. or 196° C. or 190° C. or 188° C. or 186° C. or 184° C. or 182° C. or 180° C. or 179° C., and in another embodiment, a melt temperature of at least 170° C. or at least 175° C. In another embodiment, the lower melt temperature limit is the minimum melt temperature required to obtain films described herein at the specific throughputs or specific die rates described herein.
  • In yet another embodiment of the invention, the improved extrusion properties of the films herein can be described in terms of the specific die rates; in a particular embodiment, the advantageous die rates claimed herein are maintained in a 50 mm grooved feed extruder with an L/D of 21:1 in a particular embodiment. Thus, in one embodiment, the film of the invention is formed by extruding the polymer composition temperature at a melt temperature, Tm, that satisfies the following relationship Tm≦235−3.3 (I21), at a specific die rate of from between 10 and 20 pounds of polymer per hour per inch of die circumference (0.179 to 0.357 kg/hr/mm), and in another embodiment at a specific die rate of from between 10 and 15 pounds of polymer per hour per inch of die circumference (0.179 to 0.268 kg/hr/mm). In this aspect of the invention, the melt temperatures are determined from an extrusion line suitable to form the film as described herein.
  • In general, the films of the present invention can be described as having improved melt temperatures compared to prior art bHDPEs of I21 from 4 to 20 dg/min, regardless of the method of its manufacture or the method of the manufacture of the present polyethylene compositions used to form the films of the invention. The relationship above in (I) is defined for a given set of extruder conditions. In one embodiment, this improvement is expressed more generally in the relationship Tm≦Tm x−3.3 (I21), where Tm x is the melt temperature linear extrapolated to the value of I21=0 at any given set of extruder conditions. In general, the melt temperature of the polyethylene compositions used to make the films of the invention will have values from 2 to 20° C. lower than that for prior art bHDPEs at the same (within +2 to ±3 units) of I21.
  • Another aspect of the invention is to a film comprising a polyethylene composition possessing a density of between 0.940 and 0.970 g/cm3, and an I21 value of from 4 to 20 dg/min; characterized in that the polyethylene composition extrudes at a melt temperature, Tm, that is from 2 or 4 to 10 or 20° C. less than polyethylene compositions of similar density and I12, range produced in a dual or multiple-reactor process, and extruded under the same conditions, further characterized in that the film has a gel count of less than 100. Such dual or multi-stage and -reactor processes are know in the art such as described by FP. Alt et al. in 163 MACROMOL. SYMP. 135-143 (2001) and 2 METALLOCENE-BASED POLYOLEFINS 366-378 (2000); and U.S. Pat. No. 6,407,185, U.S. Pat. No. 4,975,485, U.S. Pat. No. 4,511,704. As used herein, the term “multi-reactor polyethylene compositions” refers to polyethylene compositions produced from a staged process comprising the use of two or more reactors in tandem, or to the use of one reactor that is operated in a staged manner, as described in those references above. In this aspect of the invention, it is preferable that the melt temperature of the inventive film is compared to the “multi-reactor polyethylene composition” having an I21 value within ±3 dg/min, more preferably within ±2 dg/min, and even more preferably within ±1 dg/min.
  • In yet another aspect of the invention, the film is described as comprising a polyethylene composition, the polyethylene composition comprising a high molecular weight component having a weight average molecular weight of greater than 50,000 amu and a low molecular weight component having a weight average molecular weight of less than 40,000 amu or less than 20,000 amu or less than 15,000 amu or less than 12,000 amu; the polyethylene composition possessing a density of between 0.940 and 0.970 g/cm3, and an I21 value of less than 20 dg/min and a Mw/Mn value of from greater than 30 or 35 or 40; characterized in that the film has a gel count of less than 100. Other characteristics of the polyethylene composition may be further elucidated as described herein.
  • The quality of the films of the present invention can be characterized by the gel count, as described herein. The films have a gel count of less than 100 in one embodiment, and a gel count of less than 60 in another embodiment, and a gel count of less than 50 in another embodiment, and a gel count of less than 40 in yet another embodiment, and a gel count of less than 35 in yet another embodiment. Described alternately, the films of the present invention have an FAR value of greater than +20 in one embodiment, and greater than +30 in another embodiment, and greater than +40 in yet another embodiment. The films of the present invention can be formed with a gauge variation of from less than 16% of the total thickness in one embodiment, and less than 13% in another embodiment, and from less than 10% in yet another embodiment.
  • The polyethylene composition used to make the films of the present invention can be extruded at lower power levels and lower pressure, for a given specific throughput and melt temperature, than previously known. For a given extruder, under the same conditions, the polyethylene compositions of the present invention can be extruded at from 1 to 10% lower motor load relative to comparable bimodal polyethylene compositions having, the comparison between resins having a density of between 0.940 and 0.970 g/cm3, and an I21 value of less than 20 dg/min. In another embodiment, the improvement is from 2 to 5% lower motor load relative to comparable bimodal polyethylene compositions.
  • Stated another way, for a given extruder, the polyethylene compositions of the invention having the properties described herein extrude at a motor load of less than 80% the maximum motor load in one embodiment, and less than 77% the maximum motor load in another embodiment, and less than 75% the maximum motor load in yet another embodiment, and between 66 and 80% maximum motor load in yet another embodiment, and between 70 and 77% maximum motor load in yet another embodiment, wherein a desirable range may comprise any combination of any upper % limit with any lower % limit described herein. These advantageous properties exist while maintaining the melt temperatures and specific throughputs described herein.
  • The films of the present invention possess properties suitable for commercial use. For example the films of the invention have an MD Tensile strength of from 9,000 to 15,000 psi and a TD Tensile strength of from 9,000 to 15,000 psi in one embodiment; and an MD Tensile elongation of from 200 to 350% and TD Tensile elongation of from 200 to 350% in another embodiment, and an MD Elmendorf Tear value of from 10 to 30 g/mil in and a TD Elmendorf Tear value of from 20 to 60 g/mil in yet another embodiment; and a dart impact (F50) of greater than 150 g in one embodiment, and greater than 170 g in another embodiment. These values are determined under the test methods described further herein.
  • In one embodiment of the films of the invention, the polyethylene composition used to produce the films is preferably free of “hard foulant” material. These “hard foulants” are zones of inhomogeneous material within the polyethylene composition matrix that have distinct characteristics. In one embodiment, the hard gels have a melting point (DSC) of from 125° C. to 133° C., and from 126° C. to 132° C. in another embodiment; and further, the hard gels have a I21 of less than 0.5 dg/min in one embodiment, and less than 0.4 dg/min in another embodiment; and also have an η (0.1 rad/sec at 200° C.) value of from greater than 1000 Mpoise in one embodiment, and greater than 1200 Mpoise in another embodiment; wherein the hard gels can be characterized by any one or combination of these features. By “free of hard foulant material”, it is meant that the hard gels are present, if at all, in an amount no greater than 1 wt % by weight of the total polyethylene composition in one embodiment, and less than 0.01 wt % in another embodiment, and less than 0.001 wt % in yet another embodiment.
  • Any desirable method of olefin polymerization—for example, gas phase, slurry phase or solution polymerization process—that is known for the polymerization of olefins to form polyolefins is suitable for making the polyethylene composition suitable for the films of the present invention. In one embodiment, two or more reactors in series are used, such as, for example, a gas phase and slurry phase reactor in series, or two gas phase reactors in series, or two slurry phase reactors in series. In another embodiment, a single reactor; preferably, a single gas phase reactor is used. More particularly, this latter embodiment of the present invention comprises incorporating a high molecular weight (“HMW”) polyethylene into a low molecular weight (“LMW”) polyethylene, simultaneously in a single reactor, to form the polyethylene composition, in the presence of polymerizable monomers and a bimetallic catalyst composition. The “polyethylene composition” in one embodiment is a bimodal polyethylene composition, wherein from greater than 80 wt %, preferably greater than 90% of the monomer derived units of the composition are ethylene and the remaining monomer units are derived from C3 to C12 olefins and diolefins, described further herein.
  • In one embodiment, the LMW polyethylene and HMW polyethylene are incorporated into one another either sequentially or simultaneously, preferably simultaneously from one, two or more reactors of any suitable description; and are incorporated into one another simultaneously in a single polymerization reactor in a particular embodiment. In a preferred embodiment of the invention, the polymerization reactor used to make the polyethylene composition is a fluidized-bed, gas phase reactor such as disclosed in U.S. Pat. Nos. 4,302,566, 5,834,571, and 5,352,749 typically comprising at least one reactor, only one reactor in a particular embodiment.
  • In one embodiment, the LMW polyethylene is a polyethylene homopolymer or copolymer comprising from 0 to 10 wt % C3 to C10 α-olefin derived units, and more particularly, a homopolymer of ethylene or copolymer of ethylene and 1-butene, 1-pentene or 1-hexene derived units. The LMW polyethylene can be characterized by a number of factors. The weight average molecular weight of the LMW polyethylene ranges from less than 50,000 amu in one embodiment, and other embodiments are described further herein.
  • In one embodiment, the HMW polyethylene is a polyethylene homopolymer or copolymer comprising from 0 to 10 wt % C3 to C10 α-olefin derived units, and more particularly, a homopolymer of ethylene or copolymer of ethylene and 1-butene, 1-pentene or 1-hexene derived units. The weight average molecular weight of the HMW polyethylene ranges from greater than 50,000 amu in one embodiment, and other embodiments as described further herein. The polyethylene composition of the invention, comprising at least the HMW and LMW polymers, can also be described by any number of parameters as described herein.
  • It is known to use polymerization catalysts in the polymerization of olefins into polyolefins. The films of the present invention can be produced by any suitable catalyst composition that provides for the production of the polyethylene compositions and films described herein. In one embodiment, the films are produced from polyethylene compositions produced from a polymerization process using one class of catalyst compounds, or a combination of two or more of a similar class of compounds in another embodiment, or a combination of two or more of differing classes of catalyst compounds in yet another embodiment. In a preferred embodiment, the films comprising the polyethylene compositions described herein are produced in a polymerization process utilizing a bimetallic catalyst composition. Such bimetallic catalyst compositions comprise at least two, preferably two, Group 3 to Group 10 metal-containing compounds, both of which may be the same or different metal with similar or differing coordination spheres, patterns of substitution at the metal center or ligands bound to the metal center. Non-limiting examples of suitable olefin polymerization catalysts, which can be combined in any number of ways to form a bimetallic catalyst composition, include metallocenes, Ziegler-Natta catalysts, metal-amido catalysts as disclosed in, for example, U.S. Pat. Nos. 6,593,438; 6,380,328, U.S. Pat. No. 6,274,684, U.S. Pat. No. 6,333,389, WO 99/01460 and WO 99/46304; and chromium catalysts such as in U.S. Pat. No. 3,324,095, including for example chromium-cyclopentadienyls, chromium oxides, chromium alkyls, supported and modified variants thereof. In another embodiment, the bimetallic catalyst composition is a combination of two or more of the same class of catalyst compounds.
  • In a particular embodiment, the bimetallic catalyst composition useful in making the polymer compositions described herein comprise a metallocene and a titanium-containing Ziegler-Natta catalyst, an example of which is disclosed in U.S. Pat. No. 5,539,076, and WO 02/090393, each incorporated herein by reference. Preferably, the catalyst compounds are supported, and in a particular embodiment, both catalyst components are supported with a “primary” activator, alumoxane in a particular embodiment, the support in a particular embodiment being an inorganic oxide support.
  • In one embodiment, a metallocene catalyst component, as part of the bimetallic catalyst composition, produces the LMW polyethylene of the polyethylene composition useful for making the films. The metallocene catalyst compounds as described herein include “full sandwich” compounds having two Cp ligands (cyclopentadienyl and ligands isolobal to cyclopentadienyl) bound to at least one Group 3 to Group 12 metal atom, and one or more leaving group(s) bound to the at least one metal atom. Even more particularly, the Cp ligand(s) are selected from the group consisting of substituted and unsubstituted cyclopentadienyl ligands and ligands isolobal to cyclopentadienyl, non-limiting examples of which include cyclopentadienyl, indenyl, fluorenyl and other structures. Hereinafter, these compounds will be referred to as “metallocenes” or “metallocene catalyst components”.
  • As used herein, in reference to Periodic Table “Groups” of Elements, the “new” numbering scheme for the Periodic Table Groups are used as in the CRC HANDBOOK OF CHEMISTRY AND PHYSICS (David R. Lide ed., CRC Press 81st ed. 2000).
  • The metal atom “M” of the metallocene catalyst compound is selected from the group consisting of Groups 4, 5 and 6 atoms in one embodiment, and a Ti, Zr, Hf atoms in yet a more particular embodiment, and Zr in yet a more particular embodiment. The Cp ligand(s) form at least one chemical bond with the metal atom M to form the “metallocene catalyst compound”. In one aspect of the invention, the metallocene catalyst components of the invention are represented by the formula (II):
    CpACpBMXn  (II)
    wherein M is as described above; each X is bonded to M; each Cp group is chemically bonded to M; and n is 0 or an integer from 1 to 4, and either 1 or 2 in a particular embodiment.
  • The ligands represented by CpA and CPB in formula (II) may be the same or different cyclopentadienyl ligands or ligands isolobal to cyclopentadienyl, either or both of which may contain heteroatoms and either or both of which may be substituted by a group R. In one embodiment, CpA and CpB are independently selected from the group consisting of cyclopentadienyl, indenyl, tetrahydroindenyl, fluorenyl, and substituted derivatives of each.
  • Independently, each CpA and CpB of formula (II) may be unsubstituted or substituted with any one or combination of substituent groups R. Non-limiting examples of substituent groups R as used in structure (II) as well as ring substituents in structure (II) include hydrogen radicals, C1 to C6 alkyls, C2 to C6 alkenyls, C3 to C6 cycloalkyls, C6 to C10 aryls or alkylaryls, and combinations thereof.
  • Each X in the formula (II) and (III) is independently selected from the group consisting of halogen ions (fluoride, chloride, bromide), hydrides, C1 to C12 alkyls, C2 to C12 alkenyls, C6 to C12 aryls, C7 to C20 alkylaryls, C1 to C12 alkoxys, C6 to C16 aryloxys, C7 to C18 alkylaryloxys, C1 to C12 fluoroalkyls, C6 to C12 fluoroaryls, and C1 to C12 heteroatom-containing hydrocarbons and substituted derivatives thereof in a particular embodiment; and fluoride in yet a more particular embodiment.
  • In another aspect of the invention, the metallocene catalyst component includes those of formula (I) where CpA and CpB are bridged to each other by at least one bridging group, (A), such that the structure is represented by formula (III):
    CpA(A)CpBMXn  (III)
  • These bridged compounds represented by formula (III) are known as “bridged metallocenes”. CpA, CpB, M, X and n in structure (III) are as defined above for formula (II); and wherein each Cp ligand is bonded to M, and (A) is chemically bonded to each Cp. Non-limiting examples of bridging group (A) include divalent hydrocarbon groups containing at least one Group 13 to 16 atom, such as but not limited to at least one of a carbon, oxygen, nitrogen, silicon, aluminum, boron, germanium and tin atom and combinations thereof; wherein the heteroatom may also be C1 to C12 alkyl or aryl substituted to satisfy neutral valency. The bridging group (A) may also contain substituent groups R as defined above (for formula (II)) including halogen radicals and iron. More particular non-limiting examples of bridging group (A) are represented by C1 to C6 alkylenes, substituted C1 to C6 alkylenes, oxygen, sulfur, R′2C═, R′2Si═, —Si(R′)2Si(R′2)—, R′2Ge═, R′P═ (wherein “=” represents two chemical bonds), where R′ is independently selected from the group consisting of hydride, C1 to C10 alkyls, aryls and substituted aryls.
  • In one embodiment, a Ziegler-Natta catalyst component, as part of the bimetallic catalyst composition, produces the HMW polyethylene of the polyethylene composition useful in making the films of the present invention. Ziegler-Natta catalyst compounds are disclosed generally in ZIEGLER CATALYSTS 363-386 (G. Fink, R. Mulhaupt and H. H. Brintzinger, eds., Springer-Verlag 1995); and RE 33,683. Examples of such catalysts include those comprising Group 4, 5 or 6 transition metal oxides, alkoxides and halides, and more particularly oxides, alkoxides and halide compounds of titanium, zirconium or vanadium in combination with a magnesium compound, internal and/or external electron donors (alcohols, ethers, siloxanes, etc.), aluminum or boron alkyl and alkyl halides, and inorganic oxide supports.
  • In one embodiment, the Ziegler-Natta catalyst is combined with a support material, either with or without the metallocene catalyst component. The Ziegler-Natta catalyst component can be combined with, placed on or otherwise affixed to a support in a variety of ways. In one of those ways, a slurry of the support in a suitable non-polar hydrocarbon diluent is contacted with an organomagnesium compound, which then dissolves in the non-polar hydrocarbon diluent of the slurry to form a solution from which the organomagnesium compound is then deposited onto the carrier. The organomagnesium compound can be represented by the formula RMgR′, where R′ and R are the same or different C2-C12 alkyl groups, or C4-C10 alkyl groups, or C4-C8 alkyl groups. In at least one specific embodiment, the organomagnesium compound is dibutyl magnesium.
  • The organomagnesium and alcohol-treated slurry is then contacted with a transition metal compound in one embodiment. Suitable transition metal compounds are compounds of Group 4 and 5 metals that are soluble in the non-polar hydrocarbon used to form the silica slurry in a particular embodiment. Non-limiting examples of suitable Group 4, 5 or 6 transition metal compounds include, for example, titanium and vanadium halides, oxyhalides or alkoxyhalides, such as titanium tetrachloride (TiCl4), vanadium tetrachloride (VCl4) and vanadium oxytrichloride (VOCl3), and titanium and vanadium alkoxides, wherein the alkoxide moiety has a branched or unbranched alkyl group of 1 to 20 carbon atoms, in a particular embodiment from 1 to 6 carbon atoms. Mixtures of such transition metal compounds may also be used. In a preferred embodiment, TiCl4 or TiCl3 is the starting transition metal compound used to form the magnesium-containing Ziegler-Natta catalyst.
  • In one embodiment, the Ziegler-Natta catalyst is contacted with an electron donor, such as tetraethylorthosilicate (TEOS), an ether such as tetrahydrofuran, or an organic alcohol having the formula R″OH, where R″ is a C1-C12 alkyl group, or a C1 to C8 alkyl group, or a C2 to C4 alkyl group, and/or an ether or cyclic ether such as tetrahydrofuran.
  • The metallocene and Ziegler-Natta components may be contacted with the support in any order. In a particular embodiment of the invention, the first catalyst component is reacted first with the support as described above, followed by contacting this supported first catalyst component with a second catalyst component.
  • When combined to form the bimetallic catalyst component, the molar ratio of metal from the second catalyst component to the first catalyst component (e.g., molar ratio of Ti:Zr) is a value of from 0.1 to 100 in one embodiment; and from 1 to 50 in another embodiment, and from 2 to 20 in yet another embodiment, and from 3 to 12 in yet another embodiment; and from 4 to 10 in yet another embodiment, and from 4 to 8 in yet another embodiment; wherein a desirable molar ratio of Ti component metal:Zr catalyst component metal is any combination of any upper limit with any lower limit described herein.
  • The polymerization process used to form the polyethylene compositions useful in making the films of the invention preferably comprises injecting a supported catalyst composition into the polymerization reactor. The catalyst components and activator(s) (metallocene and Ziegler-Natta components) can be combined in any suitable manner with the support, and supported by any suitable means know in the art. Preferably, the catalyst components are co-supported with at least one activator, preferably an alumoxane. Another activator, preferably an alkylaluminum, is co-injected into the polymerization reactor as a distinct component in another embodiment. In a most preferred embodiment, the bimetallic catalyst composition, preferably comprising a metallocene and Ziegler-Natta catalyst component, is injected into a single reactor, preferably a fluidized bed gas phase reactor, under polymerization conditions suitable for producing a bimodal polyethylene composition as described herein.
  • Supports, methods of supporting, modifying, and activating supports for single-site catalyst such as metallocenes is discussed in, for example, by G. G. Hlatky in 100(4) CHEM. REV. 1347-1374 (2000). The terms “support” as used herein refers to any support material, a porous support material in one embodiment, including inorganic or organic support materials. Particularly preferred support materials include silica, alumina, silica-alumina, magnesium chloride, graphite, and mixtures thereof in one embodiment. Most preferably, the support is silica. In a particular embodiment, the support is an inorganic oxide, preferably silica, having an average particle size of less than 50 μm or less than 35 μm and a pore volume of from 0.1 to 1 or 2 or 5 cm3/g.
  • The support is preferably calcined. Suitable calcining temperatures range from 500° C. to 1500° C. in one embodiment, and from 600° C. to 1200° C. in another embodiment, and from 700° C. to 1000° C. in another embodiment, and from 750° C. to 900° C. in yet another embodiment, and from 800° C. to 900° C. in yet a more particular embodiment, wherein a desirable range comprises any combination of any upper temperature limit with any lower temperature limit. Calcining may take place in the absence of oxygen and moisture by using, for example, an atmosphere of dry nitrogen. Alternatively, calcining may take place in the presence of moisture and air.
  • The support may be contacted with the other components of the catalyst system in any number of ways. In one embodiment, the support is contacted with the activator to form an association between the activator and support, or a “bound activator”. In another embodiment, the catalyst component may be contacted with the support to form a “bound catalyst component”. In yet another embodiment, the support may be contacted with the activator and catalyst component together, or with each partially in any order. The components may be contacted by any suitable means as in a solution, slurry, or solid form, or some combination thereof, and may be heated when contacted to from 25° C. to 250° C.
  • In one embodiment, the bimetallic catalyst composition comprises at least one, preferably one, type of activator. As used herein, the term “activator” is defined to be any compound or combination of compounds, supported or unsupported, which can activate a single-site catalyst compound (e.g., metallocenes, metal amido catalysts, etc.), such as by creating a cationic species from the catalyst component. Embodiments of such activators include Lewis acids such as cyclic or oligomeric poly(hydrocarbylaluminum oxides). Preferably, the activator is an alumoxane, and more preferably, an alumoxane supported on an inorganic oxide support material, wherein the support material has been calcined prior to contacting with the alumoxane.
  • An alkylaluminum is also added, preferably to the polymerization reactor, as an activator of the Ziegler-Natta component of the bimetallic catalyst in one embodiment. The alkylaluminum activator may be described by the formula AlR§ 3, wherein R§ is selected from the group consisting of C1 to C20 alkyls, C1 to C20 alkoxys, halogen (chlorine, fluorine, bromine) C6 to C20 aryls, C7 to C25 alkylaryls, and C7 to C25 arylalkyls. Non-limiting examples of alkylaluminum compounds include trimethylaluminum, triethylaluminum, triisobutylaluminum, tri-n-hexylaluminum, tri-n-octylaluminum and the like. The alkylaluminum is preferably not supported on the support material with the catalyst components and “primary” activator (e.g., alumoxane), but is a separate component added to the reactor(s).
  • The alkylaluminum compound, or mixture of compounds, such as trimethylaluminum or triethylaluminum is feed into the reactor in one embodiment at a rate of from 10 wt. ppm to 500 wt. ppm (weight parts per million alkylaluminum feed rate compared to ethylene feed rate), and from 50 wt. ppm to 400 wt. ppm in a more particular embodiment, and from 60 wt. ppm to 300 wt. ppm in yet a more particular embodiment, and from 80 wt. ppm to 250 wt. ppm in yet a more particular embodiment, and from 75 wt. ppm to 150 wt. ppm in yet another embodiment, wherein a desirable range may comprise any combination of any upper limit with any lower limit.
  • Other primary or separately injected activators known in the art may also be useful in making the bimetallic catalyst compositions described herein. Ionizing activators are well known in the art and are described by, for example, Eugene You-Xian Chen & Tobin J. Marks, Cocatalysts for Metal-Catalyzed Olefin Polymerization: Activators, Activation Processes, and Structure-Activity Relationships 100(4) CHEMICAL REVIEWS 1391-1434 (2000). Illustrative, not limiting examples of ionic ionizing activators include trialkyl substituted ammonium salts such as triethylammonium tetra(phenyl)boron and the like; N,N-dialkyl anilinium salts such as N,N-dimethylanilinium tetra(phenyl)boron and the like; dialkyl ammonium salts such as di-(isopropyl)ammonium tetra(pentafluorophenyl)boron and the like; triaryl carbonium salts (trityl salts) such as triphenylcarbonium tetra(phenyl)boron and the like; and triaryl phosphonium salts such as triphenylphosphonium tetra(phenyl)boron and the like, and their aluminum equivalents.
  • When the activator is a cyclic or oligomeric poly(hydrocarbylaluminum oxide) (i.e., “alumoxane” such as methalumoxane “MAO”), the mole ratio of activator to catalyst component ranges from 2:1 to 100,000:1 in one embodiment, and from 10:1 to 10,000:1 in another embodiment, and from 50:1 to 2,000:1 in yet another embodiment; most preferably, the alumoxane is supported on an inorganic oxide such that, once co-supported with the metallocene, is present in a molar ratio of aluminum(alumoxane): Group 4, 5 or 6 metal (metallocene) from 500:1 to 10:1, and most preferably a ratio of from 200:1 to 50:1.
  • Any suitable method (type of polymerization reactor and reactor process, i.e., gas, slurry, solution, high-pressure, etc.) of polymerizing olefins to produce polyethylene having the characteristics as described herein can be used. The reactor(s) employing the catalyst system described herein is capable of producing from greater than 500 lbs/hr (230 Kg/hr) in one embodiment, and greater than 1,000 lbs/hr (450 Kg/hr) in another embodiment, and greater than 2,000 lbs/hr (910 Kg/hr) in yet another embodiment, and greater than 10,000 lbs/hr (4500 Kg/hr) in yet another embodiment, greater than 20,000 lbs/hr (9,100 Kg/hr) in yet another embodiment, and up to 500,000 lbs/hr (230,000 Kg/hr) in yet another embodiment.
  • Preferably, the films of the present invention are extruded and cast or blown from a polyethylene composition formed from a continuous fluidized bed gas phase process, and in particular, utilizing a single fluidized bed reactor in a single stage process. This type of reactor and means for operating the reactor are well known and completely described in, for example, U.S. Pat. Nos. 4,003,712, 4,588,790, 4,302,566, 5,834,571, and 5,352,749. Alternately, the process can be carried out in a single gas phase reactor as described in U.S. Pat. Nos. 5,352,749 and 5,462,999. These later patents disclose gas phase polymerization processes wherein the polymerization medium is fluidized by the continuous flow of the gaseous monomers and alternately a “condensing agent”.
  • An embodiment of a fluid bed reactor useful in the process of forming the polyethylene of the present invention typically comprises a reaction zone and a so-called velocity reduction zone. The reaction zone comprises a bed of growing polyethylene particles, formed polyethylene particles and a minor amount of catalyst particles fluidized by the continuous flow of the gaseous monomer and optionally diluent to remove heat of polymerization through the reaction zone. Optionally, some of the re-circulated gases may be cooled and compressed to form liquids that increase the heat removal capacity of the circulating gas stream when readmitted to the reaction zone. A suitable rate of make-up gas flow may be readily determined by simple experiment. Make up of gaseous monomer to the circulating gas stream is at a rate equal to the rate at which particulate polyethylene product and monomer associated therewith is withdrawn from the reactor and the composition of the gas passing through the reactor is adjusted to maintain an essentially steady state gaseous composition within the reaction zone. The gas leaving the reaction zone is passed to the velocity reduction zone where entrained particles are removed. Finer entrained particles and dust may be removed in a cyclone and/or fine filter. The gas is passed through a recycle line and then through a heat exchanger wherein the heat of polymerization is removed, compressed in a compressor and then returned to the reaction zone. So called “control agents” (e.g., tetrahydrofuran, isopropyl alcohol, molecular oxygen, phenol compounds, ethoxylated amines, etc) may be added to any part of the reactor system as described herein, and in a particular embodiment are introduced into the recycle line, preferably at from 0.1 to 50 wt ppm, and in even a more particular embodiment, introduced into the recycle line upstream of the heat exchanger. These agents are known to aid in reduction of electrostatic charge and/or reactor fouling at the expanded region, recycle line, bottom plate, etc.
  • In one embodiment, the fluidized bulk density of the polyethylene composition forming in the reactor(s) ranges from 16 to 24 lbs/ft3, and from 16.5 to 20 lbs/ft3 in another embodiment. The reactor(s) useful in making the polyethylene compositions of the present invention preferably operate at a space time yield of from 5 to 20 lb/hr/ft3, and more preferably from 6 to 15 lb/hr/ft3. Further, the residence time in the reactor(s), preferably one reactor, ranges from 1 to 7 hrs, and more preferably from 1.2 to 6 hrs, and even more preferably from 1.3 to 4 hrs.
  • In the fluidized bed gas-phase reactor embodiment, the reactor temperature of the fluidized bed process herein ranges from 70° C. or 75° C. or 80° C. to 90° C. or 95° C. or 100° C. or 110° C., wherein a desirable temperature range comprises any upper temperature limit combined with any lower temperature limit described herein. In general, the reactor temperature is operated at the highest temperature that is feasible, taking into account the sintering temperature of the polyethylene product within the reactor and fouling that may occur in the reactor or recycle line(s).
  • In the fluidized bed gas-phase reactor embodiment, the gas phase reactor pressure, wherein gases may comprise hydrogen, ethylene and higher comonomers, and other gases, is between 1 (101 kPa) and 100 atm (10,132 kPa) in one embodiment, and between 5 (506 kPa) and 50 atm (5066 kPa) in another embodiment, and between 10 (1013 kPa) and 40 atm (4050 kPa) in yet another embodiment.
  • The process of the present invention is suitable for the production of homopolymers comprising ethylene derived units, and/or copolymers comprising ethylene derived units and at least one or more other olefin(s) derived units. Preferably, ethylene is copolymerized with α-olefins containing from 3 to 12 carbon atoms in one embodiment, and from 4 to 10 carbon atoms in yet another embodiment, and from 4 to 8 carbon atoms in a preferable embodiment. Even more preferably, ethylene is copolymerized with 1-butene or 1-hexene, and most preferably, ethylene is copolymerized with 1-butene to form the polyethylene composition useful for the films of the invention.
  • The comonomer may be present at any level that will achieve the desired weight percent incorporation of the comonomer into the finished resin. In one embodiment of polyethylene production, the comonomer is present with ethylene in the circulating gas stream in a mole ratio range of from 0.005 (comonomer:ethylene) to 0.100, and from 0.0010 to 0.050 in another embodiment, and from 0.0015 to 0.040 in yet another embodiment, and from 0.018 to 0.035 in yet another embodiment.
  • Hydrogen gas may also be added to the polymerization reactor(s) to control the final properties (e.g., I21 and/or I2, bulk density) of the polyethylene composition. In one embodiment, the mole ratio of hydrogen to total ethylene monomer (H2:C2) in the circulating gas stream is in a range of from 0.001 or 0.002 or 0.003 to 0.014 or 0.016 or 0.018 or 0.024, wherein a desirable range may comprise any combination of any upper mole ratio limit with any lower mole ratio limit described herein. Expressed another way, the amount of hydrogen in the reactor at any time may range from 1000 ppm to 20,000 ppm in one embodiment, and from 2000 to 10,000 in another embodiment, and from 3000 to 8,000 in yet another embodiment, and from 4000 to 7000 in yet another embodiment, wherein a desirable range may comprise any upper hydrogen limit with any lower hydrogen limit described herein.
  • The bimetallic catalyst composition may be introduced into the polymerization reactor by any suitable means regardless of the type of polymerization reactor used. In one embodiment, the bimetallic catalyst composition is feed to the reactor in a substantially dry state, meaning that the isolated solid form of the catalyst has not been diluted or combined with a diluent prior to entering the reactor. In another embodiment, the catalyst composition is combined with a diluent and feed to the reactor; the diluent in one embodiment is an alkane such as a C4 to C20 alkane, toluene, xylene, mineral or silicon oil, or combinations thereof, such as described in, for example, U.S. Pat. No. 5,290,745.
  • The bimetallic catalyst composition may be combined with up to 2.5 wt % of a metal-fatty acid compound in one embodiment, such as, for example, an aluminum stearate, based upon the weight of the catalyst system (or its components), such as disclosed in U.S. Pat. No. 6,608,153. Other suitable metals useful in combination with the fatty acid include other Group 2 and Group 5-13 metals. In an alternate embodiment, a solution of the metal-fatty acid compound is fed into the reactor. In yet another embodiment, the metal-fatty acid compound is mixed with the catalyst and fed into the reactor separately. These agents may be mixed with the catalyst or may be fed into the reactor in a solution or a slurry with or without the catalyst system or its components.
  • In another embodiment, the supported catalyst(s) are combined with the activators and are combined, such as by tumbling and other suitable means, with up to 2.5 wt % (by weight of the catalyst composition) of an antistatic agent, such as an ethoxylated or methoxylated amine, an example of which is Kemamine AS-990 (ICI Specialties, Bloomington Del.).
  • The polyethylene compositions described herein are multimodal or bimodal in one embodiment, preferably bimodal, and comprise at least one HMW polyethylene and at least one LMW polyethylene in a particular embodiment. The term “bimodal,” when used to describe the polyethylene composition, means “bimodal molecular weight distribution,” which term is understood as having the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents. For example, a single polyethylene composition that includes polyolefins with at least one identifiable high molecular weight distribution and polyolefins with at least one identifiable low molecular weight distribution is considered to be a “bimodal” polyolefin, as that term is used herein. Those high and low molecular weight polymers may be identified by deconvolution techniques known in the art to discern the two polymers from a broad or shouldered GPC curve of the bimodal polyolefins of the invention, and in another embodiment, the GPC curve of the bimodal polymers of the invention may display distinct peaks with a trough as shown in the examples in FIGS. 3-5. The polyethylene compositions of the invention may be characterized by a combination of features.
  • In one embodiment, the polyethylene composition is a poly(ethylene-co-1-butene) or a poly(ethylene-co-1-hexene), preferably poly(ethylene-co-1-butene), the comonomer present from 0.1 to 5 mole percent of the polymer composition, primarily on the LMW polyethylene of the polyethylene composition.
  • The polyethylene compositions of the invention have a density in the range of 0.940 g/cm3 to 0.970 g/cm3 in one embodiment, in the range of from 0.942 g/cm3 to 0.968 g/cm3 in another embodiment, and in the range of from 0.943 g/cm3 to 0.965 g/cm3 in yet another embodiment, and in the range of from 0.944 g/cm3 to 0.962 g/cm3 in yet another embodiment, wherein a desirable density range of the polyethylene compositions of the invention comprise any combination of any upper density limit with any lower density limit described herein.
  • The polyethylene compositions of the present invention can be characterized by their molecular weight characteristics such as measured by GPC, described herein. The polyethylene compositions of the invention have an number average molecular weight (Mn) value of from 2,000 to 70,000 in one embodiment, and from 10,000 to 50,000 in another embodiment, and an weight average molecular weight (Mw) of from 50,000 to 2,000,000 in one embodiment, and from 70,000 to 1,000,000 in another embodiment, and from 80,000 to 800,000 in yet another embodiment. The bimodal polyolefins of the present invention also have a z-average molecular weight (Mz) value ranging from greater than 200,000 in one embodiment, and from greater than 800,000 in another embodiment, and from greater than 900,000 in one embodiment, and from greater than 1,000,000 in one embodiment, and greater than 1,100,000 in another embodiment, and from greater than 1,200,000 in yet another embodiment, and from less than 1,500,000 in yet another embodiment; wherein a desirable range of Mn, Mw or Mz comprises any combination of any upper limit with any lower limit as described herein.
  • The polyethylene compositions of the invention have a molecular weight distribution, a weight average molecular weight to number average molecular weight (Mw/Mn), or “Polydispersity index”, of from greater than 30 or 40 in a preferable embodiment; and a range of from 30 to 250 in one embodiment, and from 35 to 220 in another embodiment, and from 40 to 200 in yet another embodiment, wherein a desirable embodiment comprises any combination of any upper limit with any lower limit described herein. The polyethylene compositions also have a “z-average” molecular weight distribution (Mz/Mw) of from 2 to 20 in one embodiment, from 3 to 20 in another embodiment, and from 4 to 10 in another embodiment, and from 5 to 8 in yet another embodiment, and from 3 to 10 in yet another embodiment, wherein a desirable range may comprise any combination of any upper limit with any lower limit.
  • The polyethylene composition of the present invention possess a melt index (MI, or I2 as measured by ASTM-D-1238-E 190° C./2.16 kg) in the range from 0.01 dg/min to 50 dg/min in one embodiment, and from 0.02 dg/min to 10 dg/min in another embodiment, and from 0.03 dg/min to 2 dg/min in yet another embodiment, wherein a desirable range may comprise any upper limit with any lower limit described herein. The polyethylene compositions of the invention possess a flow index (FI or I21 as measured by ASTM-D-1238-F, 190° C./21.6 kg) ranging from 4 to 20 dg/min in one embodiment, and from 4 to 18 dg/min in another embodiment, and from 5 to 16 dg/min in yet another embodiment, and from 6 to 14 dg/min in yet another embodiment; and a range of from 6 to 12 dg/min in yet another embodiment, wherein a desirable I21 range may comprise any upper limit with any lower limit described herein. The polyethylene compositions in certain embodiments have a melt index ratio (I21/I2) of from 80 to 400, and from 90 to 300 in another embodiment, and from 100 to 250 in yet another embodiment, and from 120 to 220 in yet another embodiment, wherein a desirable I21/I2 range may comprise any combination of any upper limit with any lower limit described herein.
  • In another embodiment, the polyethylene compositions comprise greater than 50 wt % by weight of the total composition of HMW polyethylene, and greater than 55 wt % in another embodiment, and in another embodiment, between 50 and 80 wt %, and between 55 and 75 wt % in yet another embodiment, and between 55 and 70 wt % in yet another embodiment, the weight percentages determined from GPC measurements.
  • Further, the polyethylene compositions of the invention possess a dynamic viscosity η at 200° C. and 0.1/sec of from 100 kPoise to 3000 kPoise in one embodiment, 300 kPoise to 1400 kPoise in another embodiment, from 350 kPoise to 1000 kPoise in another embodiment, and from 400 kPoise to 800 kPoise in another embodiment, and from 500 kPoise to 700 kPoise in yet another embodiment. Dynamic viscosity in the examples herein was measured according to ASTM D4440-95 using a nitrogen atmosphere, 1.5 mm die gap and 25 mm parallel plates at 200° C. and 0.1/sec.
  • In another aspect of the invention, the polyethylene composition useful for making the films has an elasticity of greater than 0.60, and greater than 0.61 in another embodiment, and greater than 0.62 in yet another embodiment, and greater than 0.63 in yet another embodiment.
  • The individual components of the polyethylene composition may also be described by certain embodiments, and in one embodiment, the polyethylene composition comprises one HMW polyethylene and one LMW polyethylene; and in another embodiment, the polyethylene composition consists essentially of one HMW polyethylene and one LMW polyethylene.
  • In one embodiment, the molecular weight distribution (Mw/Mn) of the HMW polyethylene ranges from 3 to 24, and ranges from 4 to 24 in another embodiment, and from 6 to 18 in another embodiment, and from 7 to 16 in another embodiment, and from 8 to 14 in yet another embodiment, wherein a desirable range comprises any combination of any upper limit with any lower limit described herein. The HMW polyethylene has a weight average molecular weight ranging from greater than 50,000 amu in one embodiment, and ranging from 50,000 to 1,000,000 amu in one embodiment, and from 80,000 to 900,000 amu in another embodiment, and from 100,000 to 800,000 amu in another embodiment, and from 250,000 to 700,000 amu in another embodiment, wherein a desirable range comprises any combination of any upper limit with any lower limit described herein. The weight fraction of the HMW polyethylene in the polyethylene composition ranges may be at any desirable level depending on the properties that are desired in the polyethylene composition; in one embodiment the HMW polyethylene weight fraction ranges from 0.3 to 0.7; and from 0.4 to 0.6 in another particular embodiment, and ranges from 0.5 and 0.6 in yet another particular embodiment.
  • In one embodiment, the molecular weight distribution (Mw/Mn) of the LMW polyethylene ranges from 1.8 to 6, and from 2 to 5 in another embodiment, and from 2.5 to 4 in yet another embodiment, wherein a desirable range comprises any combination of any upper limit with any lower limit described herein. The LMW polyethylene has a weight average molecular weight ranging from 2,000 to 50,000 amu in one embodiment, and from 3,000 to 40,000 in another embodiment, and from 4,000 to 30,000 amu in yet another embodiment wherein a desirable range of LMW polyethylene in the polyethylene composition comprises any combination of any upper limit with any lower limit described herein. In another embodiment, the weight average molecular weight of the LMW polyethylene is less than 50,000 amu, and less than 40,000 amu in another embodiment, and less than 30,000 amu in yet another embodiment, and less than 20,000 amu in yet another embodiment, and less than 15,000 amu in yet another embodiment, and less than 13,000 amu in yet another embodiment. The LMW polyethylene has an I2 value of from 0.1 to 10,000 dg/min in one embodiment, and from 1 to 5,000 dg/min in another embodiment, and from 100 to 3,000 dg/min in yet another embodiment; and an I21 of from 2.0 to 300,000 dg/min in one embodiment, from 20 to 150,000 dg/min in another embodiment, and from 30 to 15,000 dg/min in yet another embodiment; wherein for the I2 and I21 values, a desirable range comprises any combination of any upper limit with any lower limit described herein. The I2 and I21 of the LMW polyethylene may be determined by any technique known in the art; and in one embodiment is determined by deconvolution of the GPC curve.
  • Granules of polyethylene material are formed from the processes described herein in making the polyethylene composition. Optionally, one or more additives may be blended with the polyethylene composition. With respect to the physical process of producing the blend of polyethylene and one or more additives, sufficient mixing should take place to assure that a uniform blend will be produced prior to conversion into a finished film product. One method of blending the additives with the polyolefin is to contact the components in a tumbler or other physical blending means, the polyolefin being in the form of reactor granules. This can then be followed, if desired, by melt blending in an extruder. Another method of blending the components is to melt blend the polyolefin pellets with the additives directly in an extruder, Brabender or any other melt blending means, preferably an extruder. Examples of suitable extruders include those made by Farrel and Kobe. While not expected to influence the measured properties of the polyethylene compositions described herein, the density, rheological and other properties of the polyethylene compositions described in the Examples are measured after blending additives with the compositions.
  • Non-limiting examples of additives include processing aids such as fluoroelastomers, polyethylene glycols and polycaprolactones, antioxidants, nucleating agents, acid scavengers, plasticizers, stabilizers, anticorrosion agents, blowing agents, other ultraviolet light absorbers such as chain-breaking antioxidants, etc., quenchers, antistatic agents, slip agents, pigments, dyes and fillers and cure agents such as peroxide.
  • In particular, antioxidants and stabilizers such as organic phosphites, hindered amines, and phenolic antioxidants may be present in the polyolefin compositions of the invention from 0.001 to 2 wt % in one embodiment, and from 0.01 to 1 wt % in another embodiment, and from 0.05 to 0.8 wt % in yet another embodiment; described another way, from 1 to 5000 ppm by weight of the total polymer composition, and from 100 to 3000 ppm in a more particular embodiment. Non-limiting examples of organic phosphites that are suitable are tris(2,4-di-tert-butylphenyl)phosphite (IRGAFOS 168) and di(2,4-di-tert-butylphenyl)pentaerithritol diphosphite (ULTRANOX 626). Non-limiting examples of hindered amines include poly[2-N,N′-di(2,2,6,6-tetramethyl-4-piperidinyl)-hexanediamine-4-(1-amino-1,1,3,3-tetramethylbutane)symtriazine] (CHIMASORB 944); bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate (TINUVIN 770). Non-limiting examples of phenolic antioxidants include pentaerythrityl tetrakis(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (IRGANOX 1010); 1,3,5-Tri(3,5-di-tert-butyl-4-hydroxybenzyl-isocyanurate (IRGANOX 3114); tris(nonylphenyl)phosphite (TNPP); and Octadecyl-3,5-Di-(tert)-butyl-4-hydroxyhydrocinnamate (IRGANOX 1076); other additives include those such as zinc stearate and zinc oleate.
  • Fillers may be present from 0.01 to 5 wt % in one embodiment, and from 0.1 to 2 wt % of the composition in another embodiment, and from 0.2 to 1 wt % in yet another embodiment and most preferably, between 0.02 and 0.8 wt %. Desirable fillers include but not limited to titanium dioxide, silicon carbide, silica (and other oxides of silica, precipitated or not), antimony oxide, lead carbonate, zinc white, lithopone, zircon, corundum, spinel, apatite, Barytes powder, barium sulfate, magnesiter, carbon black, acetylene black, dolomite, calcium carbonate, talc and hydrotalcite compounds of the ions Mg, Ca, or Zn with Al, Cr or Fe and CO3 and/or HPO4, hydrated or not; quartz powder, hydrochloric magnesium carbonate, glass fibers, clays, alumina, and other metal oxides and carbonates, metal hydroxides, chrome, phosphorous and brominated flame retardants, antimony trioxide, silica, silicone, and blends thereof. These fillers may particularly include any other fillers and porous fillers and supports known in the art.
  • In total, fillers, antioxidants and other such additives are preferably present to less than 2 wt % in the polyethylene compositions of the present invention, preferably less than 1 wt %, and most preferably to less than 0.8 wt % by weight of the total composition.
  • In one embodiment, an oxidizing agent is also added during the pelletizing step as a reactive component with the polyethylene composition. In this aspect of the polyethylene compositions of the invention, the compositions are extruded with an oxidizing agent, preferably oxygen, as disclosed in WO 03/047839. In one embodiment, from 0.01 or 0.1 or 1 to 14 or 16 SCFM (standard cubic feet per minute) of oxygen is added to the polyethylene composition during extrusion to form the film, the exact amount depending upon the type of extruder used and other conditions. Stated alternately, from between 10 and 21% by volume of oxygen in an inert gas such as nitrogen is introduced to the extruding polymer composition in one embodiment. In one embodiment, enough oxygen is added to the extruder to raise the I21/I2 value of the polyethylene composition from the reactor(s) by from 1 to 40%, and from 5 to 25% in another embodiment. The pellets produced therefrom are then used to extrude the films of the invention in a separate line, for example, and Alpine line.
  • The resultant pelletized polyethylene compositions, with or without additives, are processed by any suitable means for forming films: film blowing or casting and all methods of film formation to achieve, for example, uniaxial or biaxial orientation such as described in PLASTICS PROCESSING (Radian Corporation, Noyes Data Corp. 1986). In a particularly preferred embodiment, the polyethylene compositions of the present invention are formed into films such as described in the FILM EXTRUSION MANUAL, PROCESS, MATERIALS, PROPERTIES (TAPPI, 1992). Even more particularly, the films of the present invention are blown films, the process for which is described generally in FILM EXTRUSION MANUAL, PROCESS, MATERIALS, PROPERTIES pp. 16-29, for example.
  • Any extruder suitable for extrusion of a HDPE (density greater than 0.940 g/cm3) operating under any desirable conditions for the polyethylene compositions described herein can be used to produce the films of the present invention. Such extruders are known to those skilled in the art. Such extruders include those having screw diameters ranging from 30 to 150 mm in one embodiment, and from 35 to 120 mm in another embodiment, and having an output of from 100 to 1,500 lbs/hr in one embodiment, and from 200 to 1,000 lbs/hr in another embodiment. In one embodiment, a grooved feed extruder is used. The extruder may possess a L/D ratio of from 80:1 to 2:1 in one embodiment, and from 60:1 to 6:1 in another embodiment, and from 40:1 to 12:1 in yet another embodiment, and from 30:1 to 16:1 in yet another embodiment.
  • A mono or multi-layer die can be used. In one embodiment a 50 to 200 mm monolayer die is used, and a 90 to 160 mm monolayer die in another embodiment, and a 100 to 140 mm monolayer die in yet another embodiment, the die having a nominal die gap ranging from 0.6 to 3 mm in one embodiment, and from 0.8 to 2 mm in another embodiment, and from 1 to 1.8 mm in yet another embodiment, wherein a desirable die can be described by any combination of any embodiment described herein. In a particular embodiment, the advantageous specific throughputs claimed herein are maintained in a 50 mm grooved feed extruder with an L/D of 21:1 in a particular embodiment.
  • The temperature across the zones of the extruder, neck and adapter of the extruder ranges from 150° C. to 230° C. in one embodiment, and from 160° C. to 210° C. in another embodiment, and from 170° C. to 190° C. in yet another embodiment. The temperature across the die ranges from 160° C. to 250° C. in one embodiment, and from 170° C. to 230° C. in another embodiment, and from 180° C. to 210° C. in yet another embodiment.
  • Thus, the films of the present invention can be described alternately by any of the embodiments disclosed herein, or a combination of any of the embodiments described herein. Embodiments of the invention, while not meant to be limiting by, may be better understood by reference to the following examples.
  • EXAMPLES
  • The following examples relate to gas phase polymerization procedures carried out in a fluidized bed reactor capable of producing from greater than 500 lbs/hr (230 Kg/hr) at a production rate of from 8 to 40 T/hr or more, utilizing ethylene and 1-butene comonomer, resulting in production of the polyethylene composition. The tables identify various samples of resin and films made from those samples, along with the reported reaction conditions during the collection of the samples (“examples”). Various properties of the resulting resin products and film products are also identified. Examples 1 and 2 were extruded in the absence of oxygen (“non-tailored”) as described below, while the Examples 3-9 were extruded in the presence of oxygen (“oxygen tailored”) as per WO 03/047839, herein incorporated by reference. The comparative examples were made into films as received.
  • The fluidized bed of the reactor was made up of polyethylene granules. The reactor is passivated with an alkylaluminum, preferably trimethylaluminum. During each run, the gaseous feed streams of ethylene and hydrogen were introduced before the reactor bed into a recycle gas line. The injections were downstream of the recycle line heat exchanger and compressor. Liquid 1-butene comonomer was introduced before the reactor bed. The control agent (typically isopropyl alcohol), if any, that influenced resin split and helped control fouling, especially bottom plate fouling, was added before the reactor bed into a recycle gas line in gaseous or liquid form. The individual flows of ethylene, hydrogen and 1-butene comonomer were controlled to maintain target reactor conditions, as identified in each example. The concentrations of gases were measured by an on-line chromatograph.
  • The examples 1 and 2 were samples taken from a 3-4 day polymerization run on a single gas phase fluidized bed reactor having a diameter of 8 feet and a bed height (from distributor “bottom” plate to start of expanded section) of 38 feet. The examples 3-9 were samples taken from a different 3-4 day polymerization run on a single gas phase fluidized bed reactor having a diameter of 11.3 feet and a bed height (from distributor “bottom” plate to start of expanded section) of 44.6 feet.
  • In each polymerization run of the inventive examples, supported bimetallic catalyst was injected directly into the fluidized bed using purified nitrogen. Catalyst injection rates were adjusted to maintain approximately constant production rate. In each run, the catalyst used was made with silica dehydrated at 875° C., and metallocene compound Cp2MX2 wherein Cp is an n-butyl-substituted cyclopentadienyl ring, M is Zirconium; and X is fluoride. The titanium source for the Ziegler-Natta component was TiCl4.
  • During each run, the reacting bed of growing polyethylene particles was maintained in a fluidized state by a continuous flow of the make-up feed and recycle gas through the reaction zone. As indicated in the tables, each polymerization run for the inventive examples utilized a target reactor temperature (“Bed Temperature”), namely, a reactor temperature of about 95° C. During each run, reactor temperature was maintained at an approximately constant level by adjusting up or down the temperature of the recycle gas to accommodate any changes in the rate of heat generation due to the polymerization.
  • The example polymer compositions were extruded in a 4 inch Farrel (or Kobe) Continuous Mixer (4UMSD) at rate of 500 lbs/hr, specific energy input of 0.125 HP-Hr/lb to form pellets. An additive package was also added such that the Examples 1-9 polymer compositions comprising 800 ppm (IRGANOX 1010, Pentaerythrityltetrakis-3-(3,5-di-tert-butyl-4-hydroxyphenyl)-Propionate), 200 ppm (IRGAFOS 168, Tris(2,4-di-tert-butyl-phenyl)phosphite) and 1500 ppm zinc stearate. The examples 1 and 2 were extruded in a nitrogen atmosphere (0% Oxygen); examples 3-9 were extruded in the presence of an amount of oxygen as disclosed in WO 03/047839.
  • The polymer composition properties are described in the tables. The “I21:HMW:MFR” is a calculation of the I21 of the high molecular weight component from I21 and I2 data was based on the following empirical model (IV): I21 : HMW : MFR = 2.71828 - 0.33759 + 0.516577 * ln / 21 - 0.01523 * I21 I2 ( IV )
    where I21 and I2 were determined from ASTM standards described herein. The “I21:HMW:DSR” is a calculation of the I21 of the high molecular weight component from a dynamic viscosity measurement based on the following model (V):
    FI:HMW:DSR=η* 0.1*2.06694*10−8−4.40828*ln(G′ 0.1*1.09839)+5.36175*ln(G″ 0.1*1.09275)−0.383985*ln(G″ 100*1.1197)  (V)
    where
      • ηx (Poise) is the complex viscosity determined at 200° C. and a frequency of x,
      • G′x (dyne/cm2) is the real component of the shear modulus determined at 200° C. and a frequency of x, and
      • G″x (dyne/cm2) is the imaginary component of the shear modulus determined at 200° C. and a frequency (rad/sec) of x.
  • These parameters were measured on a Rheometrics Dynamic Stress Rheometer, using 25 mm parallel plates, a die gap of approximately 1.4 mm, measured, a stress of 10,000 dynes/cm2 and the procedure defined in ASTM standard D4440-01 Standard Test Method for Plastics: Dynamic Mechanical Properties: Melt Rheology determinations.
  • The examples 1 and 2 were extruded blown film line under the conditions listed in Table 2; the extruder screw being a 50 mm 21 d screw with a “LLDPE” feed section (Alpine part no. 171764). The melt temperature Tm was measured by an immersion thermocouple at the adapter section, near the exit of the extruder. Chilled air was applied to the outside of the bubble for cooling purposes.
  • Other Analytical methods are described:
      • Film gauge was measured according to ASTM D374-94 Method C;
      • FI (I21): Flow Index (I21) was measured as per ASTM D 1238 at 190° C., 21.6 kg;
      • MI (I2): Melt Index (I2) was measured as per ASTM D 1238 at 190° C., 2.16 kg;
      • MFR: Melt Flow Ratio is defined as the ratio I21/I2;
      • Density (g/cm3): was determined using chips cut from plaques compression molded in accordance with ASTM D-4703-00, conditioned in accordance with ASTM D618 Procedure A, and measured according to ASTM D1505-03;
      • Elasticity: This is internal test method and is defined as ratio of G′/G″ measured at 0.1 radians/second. G′ and G″ are measured on Stress Rheometer (200° C. using a Dynamic Stree Rheometer) when operating under oscillatory shear at a constant stress of 1000 Pa. The values of G′ and G″ at 0.1 radians/sec is selected for the elasticity number;
      • η*: Complex viscosity measured on Stress Rheometer at 0.1 radians/sec at 200° C.;
      • FAR: “Film Appearance Rating” is internal test method in which resin is extruded under standard operating guidelines and the resulting film is examined visually for surface imperfections. The film is compared to a reference set of standard film and a FAR rating is assigned based on operators assessment. This evaluation is conducted by an operator with considerable experience. The FAR reference films are available for the range of −50 to +50 and FAR ratings of +20 and better are considered commercially acceptable by customers;
      • Gel count: The equipment used consisted of an Optical Control Systems GmbH (OCS) Model ME-20 extruder, and OCS Model CR-8 cast film system, and an OCS Model FS-5 gel counter. The ME-20 extruder consists of a ¾″ standard screw with 3/1 compression ratio, and 25/1 L/D. It includes a feed zone, a compression zone, and a metering zone. The extruder utilizes all solid state controls, a variable frequency AC drive for the screw, 5 heating zones including 3 for the barrel, 1 for the melt temperature and pressure measurement zone, and one for the die. The die was a 4″ fixed lip die of a “fishtail” design, with a die gap of about 20 mils. The testing was performed by Southern Analytical, Inc., Houston Tex.
  • The cast film system includes dual stainless steel chrome plated and polished chill rolls, a machined precision air knife, rubber nip rolls that pull the film through the gel counter, and a torque driven wind up roll. The nip rolls are driven separately from the chill rolls and are controlled by speed or tension. A circulation cooling/heating system for the chill rolls was also included, and utilizes ethylene glycol. Steel SS rails, film break sensors, and other items were included. The example 3-9 and C1 films that were measured were from 1 mil (25 μm) in thickness, the comparative films C2, C3 and C5 were 2 mil (50 μm) films.
  • The gel counter consists of a digital 2048 pixel line camera, a halogen based line lighting system, an image processing computer, and Windows NT4 software. The camera/light system was mounted on the cast film system between the chill roll and nip rolls, and was set up for a 50 micron resolution on film. This means that the smallest defect that could be seen was 50 microns by 50 microns in size.
  • The pellet samples were run with constant extruder temperatures (180° C. for the feed zone, 190° C. for all remaining zones), and constant chill roll temperature of 40° C. The extruder and chill roll speeds were varied slightly between samples to provide an optimum film for each sample. With more experimentation, one set of operating conditions might be found that are satisfactory for all samples. The gel counter was set up with 10 different size classes beginning at 50-100 microns and increasing at 100 micron intervals, 4 different shape classes beginning with a perfect circular shape and increasing to more oblong shapes, and two detection levels (one for gels and one for black specks). The gel detection level or sensitivity used was 35 on a 0 to 100 scale.
  • Once the camera set up parameters were determined, the extruder was purged with the first sample (typically about 20 minutes) or until it was apparent that the test conditions were at steady state, or “equilibrium”. This was done by looking at a trend line chart of gel count number on the “y” axis, and time on the “x” axis. Tests were then run on 3 square meters of film per test, as the film moved by the camera. Three tests were run in succession on the sample, in order to determine test repeatability. At the end of each 3 square meter test, tabular results were printed. After the purge time, a set of 3 successive 3 square meter tests was performed for the second sample, and results printed.
  • All gel tests on remaining samples were conducted in this way, except that extruder speed, chill roll speed, and resultant film thickness was varied slightly on some samples. Pictures of the actual gels were also obtained throughout the testing (in what is called a “mosaic” of pictures) in order to make sure that what the analyzer was seeing was really a gel, and also to make sure that no gel were being measured twice or missed. For the granular samples, one set of operating conditions was found that was adhered to for all samples, including film thickness, so that all results could be directly comparable.
  • The gel counts reported in the tables were normalized to gauge. Each sample was tested three times. The data provided from the test was used to calculate the sum of all gels 200 microns in size or smaller. The three runs from each sample were averaged, then that average divided by the gauge in mils. The gel count results are normalized as the number of gels less than 200 μm in size contained in a 3 m2 film sample of 1 mil thickness, or a volume of 7.62×10−5 m3.
  • Dart Impact Strength, F50: Measured on film as per procedure ASTM D 1709—Method A;
      • Elmendorf Tear—Measured on Film as per ASTM D 1922;
      • 1% Secant Modulus: Measured on Film as per ASTM D 882; and
      • GPC. The Mw/Mn, Mz/Mw, the Mw (weight average molecular weight) and Mn (number average molecular weight) values, and % HMW component, etc. GPC measurements were as determined by gel permeation chromatography using crosslinked polystyrene columns; pore size sequence: 1 column less than 1000, 3 columns of mixed 5×10(7); 1,2,4-trichlorobenzene solvent at 145° C. with refractive index detection. The GPC data was deconvoluted into high and low molecular weight components by use of a “Wesslau model”, wherein the P term was restrained for the low molecular weight peak to 1.4, as described by E. Broyer & R. F. Abbott, Analysis of molecular weight distribution using multicomponent models, ACS SYMP. SER. (1982), 197 (COMPUT. APPL. APPL. POLYM. SCI.), 45-64.
  • Comparative Example 1 (“C1”) is a single reactor (gas phase) produced bimodal polyethylene having the properties listed in Tables 2 and 4. It was made using a bimetallic catalyst system similar to the catalyst composition described above for the inventive examples.
  • In order to determine the physical properties of the C1 resin, a granular sample of the C1 was obtained and blended with 1500 ppm Tetrakis[methylene(3,5-di-t-butyl-4-hydroxyhydrocinnamate)]methane, commonly known as IRGANOX 1010, 1500 ppm Tris(2,4-di-t-butylphenyl)phosphite (commonly known as IRGAFOS 168 and 1500 ppm zinc stearate. The blended material was melt homogenized under a nitrogen blanket on a laboratory scale Brabender single screw extruder. The FI, MFR and density of the melt homogenized material was measured and is reported in Table 2. Larger amounts of the same C1 were blended with 200 ppm IRGAFOS 168, 800 ppm IRGANOX 1010 and 1500 ppm zinc stearate to determine the film properties. This blend was compounded on a Farrel 18 UMSD at an SEI of 179 kW*H/tonn and 10.2% oxygen at 8.8 SCFM applied to the melt side of the flow dam. The melt homogenized product of this compounding procedure was converted into film, and the film process and physical properties are reported in Tables 3 and 4. The melt temperatures are the temperature at the downstream end of the mixing zone of the extruder.
  • Comparative Example 2 (“C2”) is a Dow UNIPOL™ II 2100 bimodal poly(ethylene-co-1-butene) produced in a two-staged dual reactor gas phase process using a Ziegler-Natta type catalyst.
  • Comparative Example 3 (“C3”) is a Mitsui HD7960 bimodal poly(ethylene-co-1-butene) produced in a two-staged slurry process, available from ExxonMobil Chemical Co.
  • Comparative Example 4 (“C4”) is a Mitsui HD7755 bimodal poly(ethylene-co-1-butene) produced in a two-staged slurry process, available from ExxonMobil Chemical Co.
  • Comparative Example 5 (“C5”) is a Alathon™ L5005 bimodal poly(ethylene-co-1-butene) produced in a two-staged process available from Equistar Chemicals.
    TABLE 1
    Process Parameters in forming the polyethylene compositions
    corresponding to examples 1 and 2, and polymer characteristics
    1 2
    Process Parameter
    amount of polymer lbs 190,000 230,000
    collected in 24 hr (±10%)
    H2/C2 Gas Ratio Mol/mol 0.011 0.011
    C4/C2 Gas Ratio Mol/mol 0.026 0.024
    C4/C2 Flow Ratio Kg/kg 0.0147 0.0152
    Ethylene partial pressure Bara 11.3 13.8
    Water/C2 Flow Ratio wt ppm 20.8 20.1
    Ti Activity Kg PE/kg 8166
    catalyst
    TMA in resin wt ppm 113 113
    Reactor temperature ° C. 95 95
    polyethylene
    composition
    I21 dg/min 8.5 8.75
    I21/I2 (MFR) 122 105
    Density g/cc 0.951 0.951
    Elasticity 0.57 0.52
    η 0.1 s−1/200°C. poise 1,001,000 811,000
    I21 HMW dg/min 0.338 0.442
    I21 HMW-DSR dg/min 0.296 0.381
    % HMW-MFR % 54 57
    % HMW-DSR % 54 55
    % HMW-GPC % 64 65
    Mn amu 3119 4504
    Mw amu 263,733 257,857
    Mz amu 1,552,131 1,296,849
    Mw/Mn (MWD) 84.54 57.24
    Mz/Mw 5.89 5.02
    LMW-Mw amu 7191 8900
    HMW-MW amu 494,890 444,430
    HMW-MWD 11 9.4
  • TABLE 2
    Film compounding conditions and film properties
    of comparative and inventive examples 1 and 2
    C4 C1 1 2
    Resin Properties
    I21 dg/min 10.6 10.9 8.5 8.75
    I21/I2 142 111 122 105
    Density g/cm3 0.951 0.948 0.951 0.951
    Elasticity 0.60 0.52 0.57 0.52
    Extruder Conditions
    Extruder Diameter mm 50 50 50 50
    Extruder L/D 21 21 21 21
    Die Diameter mm 120 120 120 120
    Die Gap mm 1.4 1.4 1.4 1.4
    AVG Extruder Set ° C. 190 190 190 190
    Temp.
    AVG Die Set Temp. ° C. 200 200 200 200
    Stabilizer Yes Yes Yes Yes
    Chilled Air Yes Yes Yes Yes
    Extrusion Properties
    Rate Lbs/hr 199.7 200.4 199.0 199.8
    Specific Die Rate Lbs/hr/in 13.5 13.5 13.4 13.5
    Melt Temperature ° C. 180.3 184 178.6 178.0
    Specific Throughput Lbs/hr/rpm 1.90 1.86 1.88 1.84
    Motor Load (relative to % 85 87 82 80
    maximum for the instrument)
    Pressure psi 7370 8065 7676 7415
    Film Properties
    BUR
    4 4 4 4
    Gauge mil 0.5 0.5 0.5 0.5
    Gauge Variation 16% 13% 27% 22%
    FAR +50 −20 +40 +40/50
    Dart Impact Strength F50 g 228 189 174 192
    Elmendorf Tear - MD g/mil 20 17 19 20
    Elmendorf Tear - TD g/mil 31 46 23 37
    1% Secant Modulus MD psi 153,000 145,000 186,000 165,000
    1% Secant Modulus TD psi 148,000 142,000 154,000 152,000
  • The examples 1 and 2, produced in a single gas phase reactor using a bimetallic catalyst as described, produced polymer compositions having the unexpected benefit of improved processability over prior single reactor bimodal resins and a dual-reactor produced bimodal resin commonly known. The lower power, as also represented in FIGS. 1 and 2, represent a dramatic improvement in film production, as the inventive polymer compositions can be more easily processed, thus improving its commercial value. This is especially so given that the I21 values for examples 1 and 2 are lower than that for both comparative examples, thus the expectation that the flow through the die to form the film would take more power, not less.
  • As an even further advantage, the melt temperature of the inventive examples 1 and 2 is significantly lower when compared to the comparative examples, thus also an improvement in processability. A melt temperature of less than 180° C., and less than 179° C. in a particular embodiment, is found in the inventive examples, while still maintaining a high specific die rate of at least 10 lbs polymer/hr/inch of die circumference and high specific throughput. Thus, if motor loads and/or pressures were applied to the inventive examples 1 and 2 comparable to the C1 and C4 examples, it is likely that the specific throughputs could be at least 1.90 lbs polyethylene/hr/rpm (0.863 kg/hr/rpm) higher at similar melt temperatures.
  • Reactor conditions for runs to produce the polyethylene compositions corresponding to film examples 3-9 are in Table 3 below. The polyethylene composition properties of those corresponding examples are found in Table 4. Film extrusion conditions for examples 3-9, and for determination of the relationship Tm≦235−3.3 (I21) and its specific embodiments, are as follows: an Alpine extruder line having a 50 mm grooved feed extruder, an L/D ratio of 21:1, a temperature profile of 180° C. flat across the extruder, and 190° C. flat across the die, 4:1 BUR (blow up ratio, the ratio of the initial bubble diameter to the die diameter) an output of 200 lbs/hr, and a 120 mm die with measured 1.4 mm die gap, using a high-density type screw design; also using single lip air ring (with cooled air) and internal bubble stabilizer; the HDPE screw being a 50 mm 21 d screw with a HDPE feed section (Alpine part no. 116882). The melt temperature Tm was measured by an immersion thermocouple at the adapter section, near the exit of the extruder. Examples 3-9 were oxygen tailored similarly to C1. The extrusion properties and film properties of examples 3-9 are found in Tables 5 and 6.
  • The examples 3-9 exhibited no detectable odor, whereas the C1 sample has some odor upon extrusion. The examples 3-9, although oxygen tailored and thus exhibiting, on average, larger I21 values and larger I2 values, still show the improvements of the invention, as these resins are also more easily processed relative to the prior art resins.
    TABLE 3
    Polymerization conditions for Examples 3 through 9
    Parameter Units 3 4 5 6 7 8 9
    Amt. PE in 24 hrs Tonnes 156 156 156 156 156 156 156
    H2/C2 mol/mol 0.0085 0.0085 0.009 0.009 0.009 0.009 0.009
    C4/C2 mol/mol 0.0272 0.0272 0.021 0.021 0.021 0.0183 0.0183
    C4/C2 flow ratio kg/kg 0.0166 0.0166 0.0122 0.0122 0.0122 0.0122 0.0122
    C2 partial pressure kPa 1400 1400 1400 1400 1400 1400 1400
    Ti activity Kg PE/kg 6766 * 5327 5927 6762 5819 5915
    catalyst
    TMA added to reactor Wt ppm 103 * 96 102 107 101 123
    Reactor temp ° C. 95 95 95 95 95 95 95

    *not recorded, expected to be approximately the same as other readings
  • TABLE 4
    Polyethylene properties in film examples
    3 through 9 and comparatives
    density
    example (g/cm3) I21 (dg/min) I21/I2 Mw/Mn elasticity
    C1 0.950 10.9 123 34 0.62
    C2 0.949 10.38 160 26 0.68
    C3 0.952 11.9 133 0.60
    C5 0.950 8.6 152 0.64
    3 0.949 8.39 137 84 0.62
    4 0.949 9.38 157 83 0.65
    5 0.949 11.12 168 90 0.62
    6 0.948 8.09 146 82 0.61
    7 0.947 8.61 146 81 0.61
    8 0.950 10.01 174 91 0.64
    9 0.951 11.5 196 110 0.65
  • TABLE 5
    Other polyethylene properties of examples 3 through 9 and comparatives
    Property Units
    3 4 5 6 7 8 9 C1 C2 C3 C5
    Resin Properties
    LMW Mw 7823 8620 8644 8698 8709 7959 6389 16311 21454
    HMW Mw 444443 480543 505190 539136 456299 494016 493254 406641 481868
    HMW MWD 8.5 7.3 7.2 7.6 6.5 7.0 12.0 6.3 4.3
  • TABLE 6
    Film properties and extrusion characteristics film examples 3 through 9 and comparatives
    Property Units 3 4 5 6 7 8 9 C1 C2 C3 C5
    Extrusion Properties
    Melt Temp ° C. 201 196 195.5 206 204 194 193 206 209 200.5 212
    Pressure psi 8550 8200 8250 8980 8780 8210 8110 8480 8200 7960 8450
    Motor Load %  77% 71%  74%  78%  77%  75% 74%  82%  82%  77%  80%
    Specific lbs/hr 1.16 1.17 1.18 1.17 1.17 1.18 1.18 1.20 1.18 1.19 1.19
    Throughput /rpm
    Gauge mil 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5
    BUR 4:1 4:1 4:1 4:1 4:1 4:1 4:1 4:1 4:1 4:1 4:1
    Film Properties
    FAR 40/50 40/50 40/50 40/50 40/50 40/50 50 20 50 50 40
    gel count 199 34 36 29 32.5 31 28 442 218 33
    DDI g 182 201 178 180 194 234 219 270 166
    MD Tear g/mil 21 24 20 22 25 21 24 17 22
    TD Tear g/mil 30 31 32 27 31 39 41 53 27
    MD Tensile psi 11632 11389 12324 11156 11140 10959 12228 11019 11406
    Strength
    TD Tensile psi 11639 10942 10404 12275 10863 10298 12746 11784 10816
    Strength
    MD Tensile % 278% 288% 251% 252% 275% 295% 299% 408% 279%
    Elongation
    TD Tensile % 278% 273% 304% 288% 259% 297% 322% 356% 385%
    Elongation
    MD Yield psi 5840 5376 6009 5786 5374 5114 5186 5325 5293
    Strength
    TD Yield psi 4697 4575 4548 4725 4568 4652 4335 4627
    Strength
    MD Yield %  3%  4%  5%  5%  5%  4%  8%  5%
    Elongation
    TD Yield %  6%  4%  4%  4%  4%  4%  5%  6%
    Elongation
  • The film quality of examples 3-9 are excellent as indicated by the high FAR values and the low gel counts. Given the equally high FAR values of examples 1 and 2, it can be inferred that they too have similarly low gel counts. Thus, the oxygen tailoring has little to no influence on film quality.
  • Further, the advantages of the films of the present invention can be seen from the data. In particular, at relatively high specific throughputs, the motor loads, expressed as a percentage of the maximum motor load allowable for the equipment used, are significantly lower—all less than 77 to 78%—for the examples 3 through 9, while that for each comparative was typically higher; further, the melt temperatures for the inventive examples were significantly lower than for most of the inventive examples. Also, it can be seen that examples 3-9 follow the relationship Tm≦235−3.3 (I21), wherein the polyethylene composition is extruded at a specific throughput of from 1 to 1.5 lbs/hr/inch, as represented graphically at FIG. 6. Further, the more general relationship Tm≦Tm x−3.3 (I21) is also followed when comparing the examples 1 and 2, and the examples 3-9, each set having been extruded under differing conditions and using a different extruder screws.
  • More particularly, the advantages of the present invention are evident by comparing the motor loads (%) and melt temperatures of the inventive example 3-9 extrusions versus the comparative examples in Table 5, and graphically in FIGS. 6 and 7. While the trend for the inventive examples is towards decreasing melt temperatures and motor loads as I21 increases, the comparative resins fall higher for both the extruder motor load and melt temperature.
  • It can be seen from the specific throughput, melt temperature and motor load data that the present invention offers a significant improvement over the prior art, even over prior disclosed single reactor bimodal products such as disclosed in H.-T. Liu et al. in 195 MACROMOL. SYMP. 309-316 (July, 2003). The processing parameters of the films in Liu et al-from resins having an I21 of 6.2 dg/min and density of 0.95 g/cm3—are not as advantageous as the films of the current invention. It should be noted, as see in the FIGS. 3-5 of the present invention, that the bimodal resins of Liu et al. are similar to the C1 above. Certainly, the present invention is shown to offer significant improvement over other prior art bimodal resins having a I21 value of less than 20 and density with the range of 0.930 and 0.970 g/cm3, this improvement quite significant when taking into account the large commercial quantities of resin being processed in commercial-scale extruders.
  • While the present invention has been described and illustrated by reference to particular embodiments, those of ordinary skill in the art will appreciate that the invention lends itself to many different variations not illustrated herein. For these reasons, then, reference should be made solely to the appended claims for purposes of determining the scope of the present invention. Further, certain features of the present invention are described in terms of a set of numerical upper limits and a set of numerical lower limits. It should be appreciated that ranges formed by any combination of these limits are within the scope of the invention unless otherwise indicated.

Claims (40)

1. A film comprising a polyethylene composition possessing a density of between 0.944 and 0.962 g/cm3, an I21 value of from 6 to 14 dg/min, and a Mw/Mn value of from greater than 35; characterized in that the polyethylene composition extrudes at a melt temperature, Tm, that satisfies the following relationship:

T m≦235−3.3(I 21)
wherein the polyethylene composition is extruded at a specific throughput of from 1.1 to 1.3 lbs/hr/rpm; and wherein the polyethylene composition formed into a film has a gel count of less than 100.
2. The film of claim 1, wherein the polyethylene composition comprises a high molecular weight component having a weight average molecular weight of greater than 50,000 amu and a low molecular weight component having a weight average molecular weight of less than 50,000 amu.
3. The film of claim 2, wherein the low molecular weight component possesses a weight average molecular weight of less than 40,000 amu.
4. The film of claim 2, wherein the low molecular weight component possesses a weight average molecular weight of less than 30,000 amu.
5. The film of claim 1, wherein fillers, antioxidants and other additives are present to less than 2 wt % in the polyethylene composition.
6. The film of claim 1, wherein the polyethylene composition has an Mw/Mn value of from greater than 40.
7. The film of claim 1, wherein polyethylene composition has a z-average molecular weight distribution of from 3 to 20.
8. The film of claim 1, wherein the polyethylene composition has an elasticity of greater than 0.60.
9. The film of claim 1, wherein the film has a gel count of less than 50.
10. The film of claim 1, wherein the polyethylene composition is produced in a single continuous gas phase reactor process.
11. A film comprising a polyethylene composition possessing a density of between 0.944 and 0.962 g/cm3, an I21 value of from 6 to 14 dg/min, and a Mw/Mn value of from greater than 35; characterized in that the polyethylene composition extrudes at a melt temperature, Tm, that satisfies the following relationship:

T m≦240−3.3(I 21)
wherein the polyethylene composition is extruded at a specific throughput of from 1.1 to 1.3 lbs/hr/rpm; and wherein the polyethylene composition formed into a film has a gel count of less than 100.
12. The film of claim 11, wherein the polyethylene composition comprises a high molecular weight component having a weight average molecular weight of greater than 50,000 amu and a low molecular weight component having a weight average molecular weight of less than 50,000 amu.
13. The film of claim 12, wherein the low molecular weight component possesses a weight average molecular weight of less than 40,000 amu.
14. The film of claim 12, wherein the low molecular weight component possesses a weight average molecular weight of less than 30,000 amu.
15. The film of claim 11, wherein fillers, antioxidants and other additives are present to less than 2 wt % in the polyethylene composition.
16. The film of claim 11, wherein the polyethylene composition has an Mw/Mn value of from greater than 40.
17. The film of claim 11, wherein polyethylene composition has a z-average molecular weight distribution of from 3 to 20.
18. The film of claim 11, wherein the polyethylene composition has an elasticity of greater than 0.60.
19. The film of claim 11, wherein the film has a gel count of less than 50.
20. The film of claim 11, wherein the polyethylene composition is produced in a single continuous gas phase reactor process.
21. A film comprising a polyethylene composition possessing a density of between 0.944 and 0.962 g/cm3, an I21 value of from 6 to 14 dg/min, and a Mw/Mn value of from greater than 35; characterized in that the polyethylene composition extrudes at a melt temperature, Tm, that satisfies the following relationship:

T m≦235−3.5(I 21)
wherein the polyethylene composition is extruded at a specific throughput of from 1.1 to 1.3 lbs/hr/rpm; and wherein the polyethylene composition formed into a film has a gel count of less than 100.
22. The film of claim 21, wherein the polyethylene composition comprises a high molecular weight component having a weight average molecular weight of greater than 50,000 amu and a low molecular weight component having a weight average molecular weight of less than 50,000 amu.
23. The film of claim 22, wherein the low molecular weight component possesses a weight average molecular weight of less than 40,000 amu.
24. The film of claim 22, wherein the low molecular weight component possesses a weight average molecular weight of less than 30,000 amu.
25. The film of claim 21, wherein fillers, antioxidants and other additives are present to less than 2 wt % in the polyethylene composition
26. The film of claim 21, wherein the polyethylene composition has an Mw/Mn value of from greater than 40.
27. The film of claim 21, wherein polyethylene composition has a z-average molecular weight distribution of from 3 to 20.
28. The film of claim 21, wherein the polyethylene composition has an elasticity of greater than 0.60.
29. The film of claim 21, wherein the film has a gel count of less than 50.
30. The film of claim 21, wherein the polyethylene composition is produced in a single continuous gas phase reactor process.
31. A film comprising a polyethylene composition possessing a density of between 0.944 and 0.962 g/cm3, an I21 value of from 6 to 14 dg/min, and a Mw/Mn value of from greater than 35; characterized in that the polyethylene composition extrudes at a melt temperature, Tm, that satisfies the following relationship:

T m≦240−3.5 (I 21)
wherein the polyethylene composition is extruded at a specific throughput of from 1.1 to 1.3 lbs/hr/rpm; and wherein the polyethylene composition formed into a film has a gel count of less than 100.
32. The film of claim 31, wherein the polyethylene composition comprises a high molecular weight component having a weight average molecular weight of greater than 50,000 amu and a low molecular weight component having a weight average molecular weight of less than 50,000 amu.
33. The film of claim 32, wherein the low molecular weight component possesses a weight average molecular weight of less than 40,000 amu.
34. The film of claim 32, wherein the low molecular weight component possesses a weight average molecular weight of less than 30,000 amu.
35. The film of claim 31, wherein fillers, antioxidants and other additives are present to less than 2 wt % in the polyethylene composition
36. The film of claim 31, wherein the polyethylene composition has an Mw/Mn value of from greater than 40.
37. The film of claim 31, wherein polyethylene composition has a z-average molecular weight distribution of from 3 to 20.
38. The film of claim 31, wherein the polyethylene composition has an elasticity of greater than 0.60.
39. The film of claim 31, wherein the film has a gel count of less than 50.
40. The film of claim 31, wherein the polyethylene composition is produced in a single continuous gas phase reactor process.
US11/007,863 2003-12-05 2004-12-09 Polyethylene films Expired - Fee Related US7090927B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US11/007,863 US7090927B2 (en) 2003-12-05 2004-12-09 Polyethylene films

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US52748003P 2003-12-05 2003-12-05
US10/781,404 US6878454B1 (en) 2003-12-05 2004-02-18 Polyethylene films
US11/007,863 US7090927B2 (en) 2003-12-05 2004-12-09 Polyethylene films

Related Parent Applications (1)

Application Number Title Priority Date Filing Date
US10/781,404 Continuation US6878454B1 (en) 2003-12-05 2004-02-18 Polyethylene films

Publications (2)

Publication Number Publication Date
US20050154168A1 true US20050154168A1 (en) 2005-07-14
US7090927B2 US7090927B2 (en) 2006-08-15

Family

ID=34426342

Family Applications (3)

Application Number Title Priority Date Filing Date
US10/781,404 Expired - Lifetime US6878454B1 (en) 2003-12-05 2004-02-18 Polyethylene films
US11/008,021 Expired - Fee Related US7101629B2 (en) 2003-12-05 2004-12-09 Polyethylene films
US11/007,863 Expired - Fee Related US7090927B2 (en) 2003-12-05 2004-12-09 Polyethylene films

Family Applications Before (2)

Application Number Title Priority Date Filing Date
US10/781,404 Expired - Lifetime US6878454B1 (en) 2003-12-05 2004-02-18 Polyethylene films
US11/008,021 Expired - Fee Related US7101629B2 (en) 2003-12-05 2004-12-09 Polyethylene films

Country Status (18)

Country Link
US (3) US6878454B1 (en)
EP (1) EP1692195B1 (en)
JP (1) JP4662946B2 (en)
KR (1) KR101085329B1 (en)
CN (1) CN1890271B (en)
AR (1) AR045633A1 (en)
AT (1) ATE421543T1 (en)
AU (1) AU2004303753B2 (en)
BR (1) BRPI0417355A8 (en)
CA (1) CA2546368A1 (en)
DE (1) DE602004019245D1 (en)
ES (1) ES2320142T3 (en)
MX (1) MXPA06006403A (en)
MY (1) MY137613A (en)
PL (1) PL1692195T3 (en)
RU (1) RU2349611C2 (en)
TW (1) TWI342883B (en)
WO (1) WO2005061561A1 (en)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20090246433A1 (en) * 2004-12-17 2009-10-01 Michie William J Rheology modified relatively high melt strength polyethylene compositions and methods of making pipes, films, sheets, and blow-molded articles
US20100105849A1 (en) * 2007-03-30 2010-04-29 Univation Technologies, Llc Systems and methods for fabricating polyolefins
CN105086095A (en) * 2014-04-24 2015-11-25 中国石油化工股份有限公司 Polyethylene composition and preparation method thereof, and gas permeable film prepared from polyethylene composition

Families Citing this family (53)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20050200046A1 (en) * 2004-03-10 2005-09-15 Breese D. R. Machine-direction oriented multilayer films
EP1584852B1 (en) * 2004-04-03 2011-10-19 Borealis Technology Oy A pressureless polymer pipe
US20050245687A1 (en) * 2004-04-30 2005-11-03 Appel Marvin R Multimodal polyethylene extrusion
US7193017B2 (en) * 2004-08-13 2007-03-20 Univation Technologies, Llc High strength biomodal polyethylene compositions
US8202940B2 (en) * 2004-08-19 2012-06-19 Univation Technologies, Llc Bimodal polyethylene compositions for blow molding applications
US7285617B2 (en) * 2004-10-08 2007-10-23 Exxonmobil Chemical Patents Inc. Oxygen tailoring of polyethylene blow molding resins
DE102005009896A1 (en) * 2005-03-01 2006-09-07 Basell Polyolefine Gmbh Polyethylene molding compound for producing blown films with improved mechanical properties
WO2006107373A1 (en) * 2005-03-31 2006-10-12 Exxonmobil Chemical Patents Inc. Processes for producing high density polyethylene
CA2505894A1 (en) * 2005-04-29 2006-10-29 Nova Chemicals Corporation Method for reducing dusting in hdpe
US6995235B1 (en) * 2005-05-02 2006-02-07 Univation Technologies, Llc Methods of producing polyolefins and films therefrom
US20060275571A1 (en) * 2005-06-02 2006-12-07 Mure Cliff R Polyethylene pipes
US20070010626A1 (en) * 2005-07-11 2007-01-11 Shankernarayanan Manivakkam J Polyethylene compositions
US7625982B2 (en) * 2005-08-22 2009-12-01 Chevron Phillips Chemical Company Lp Multimodal polyethylene compositions and pipe made from same
CA2620083C (en) * 2005-08-24 2014-07-15 Dow Global Technologies Inc. Polyolefin compositions, articles made therefrom and methods for preparing the same
US20070049711A1 (en) 2005-09-01 2007-03-01 Chi-I Kuo Catalyst compositions comprising support materials having an improved particle-size distribution
US20090099315A1 (en) * 2005-11-28 2009-04-16 Basell Polyolefine Gmbh Polyethylene Composition Suitable for the Preparation of Films and Process for Preparing the Same
US7595364B2 (en) * 2005-12-07 2009-09-29 Univation Technologies, Llc High density polyethylene
AU2007225248B2 (en) 2006-03-10 2012-04-19 Dow Global Technologies Llc Polyethylene resins for sheet and thermoforming applications
EP1834983A1 (en) * 2006-03-14 2007-09-19 Ineos Europe Limited Polymer films
US20080051538A1 (en) * 2006-07-11 2008-02-28 Fina Technology, Inc. Bimodal pipe resin and products made therefrom
US7893181B2 (en) * 2006-07-11 2011-02-22 Fina Technology, Inc. Bimodal film resin and products made therefrom
CA2568454C (en) * 2006-11-17 2014-01-28 Nova Chemicals Corporation Barrier film for food packaging
US7601787B2 (en) * 2006-11-30 2009-10-13 Equistar Chemicals, IP Ethylene polymerization process
US20090297810A1 (en) * 2008-05-30 2009-12-03 Fiscus David M Polyethylene Films and Process for Production Thereof
RU2509782C2 (en) * 2008-09-25 2014-03-20 Базелль Полиолефине Гмбх Impact-resistant linear low density polyethylene and films made therefrom
MX2011003161A (en) * 2008-09-25 2011-05-19 Basell Polyolefine Gmbh Impact resistant lldpe composition and films made thereof.
KR20110061584A (en) * 2008-09-25 2011-06-09 바젤 폴리올레핀 게엠베하 Impact resistant lldpe composition and films made thereof
EP2326678A1 (en) * 2008-09-25 2011-06-01 Basell Polyolefine GmbH Impact resistant lldpe composition and films made thereof
WO2010034464A1 (en) * 2008-09-25 2010-04-01 Basell Polyolefine Gmbh Impact resistant lldpe composition and films made thereof
US20100210797A1 (en) * 2009-02-17 2010-08-19 Fina Technology, Inc. Polyethylene Films having Improved Barrier Properties
KR20120024815A (en) * 2009-05-29 2012-03-14 스미또모 가가꾸 가부시끼가이샤 ETHYLENE-α-OLEFIN COPOLYMER, MOLDED ARTICLE, CATALYST FOR COPOLYMERIZATION, AND METHOD FOR PRODUCING ETHYLENE-α-OLEFIN COPOLYMER
EP2354167A1 (en) 2010-02-05 2011-08-10 Total Petrochemicals Research Feluy Bimodal polyethylene for blow-moulding applications.
EA025606B1 (en) 2010-02-05 2017-01-30 Тотал Рисерч Энд Текнолоджи Фелюй Process for preparing polyolefin
RU2462479C2 (en) * 2010-04-15 2012-09-27 Учреждение Российской Академии Наук Институт Проблем Химической Физики Ран (Ипхф Ран) Catalyst for polymerisation and copolymerisation of ethylene, preparation method thereof and method of producing polyethylenes using said catalyst
US8383754B2 (en) 2010-04-19 2013-02-26 Chevron Phillips Chemical Company Lp Catalyst compositions for producing high Mz/Mw polyolefins
ES2660556T3 (en) * 2011-04-11 2018-03-22 Total Research & Technology Feluy Recycling of high density polyethylene from household polymer waste
BR112014029739B1 (en) * 2012-05-30 2021-01-12 Ineos Europe Ag polymeric composition for blow molding
BR112014025580B1 (en) * 2012-06-26 2022-04-05 Dow Global Technologies Llc POLYETHYLENE MIXTURE-COMPOSITION SUITABLE FOR BLOWING FILM
US9481772B2 (en) * 2012-06-26 2016-11-01 Ineos Europe Ag Film composition
JP2014088476A (en) * 2012-10-29 2014-05-15 Hosokawa Yoko Co Ltd Polyethylene film, laminate and container
DE102013020293A1 (en) * 2013-12-09 2015-06-11 Bowcraft Gmbh vapor barrier
GB2533770B (en) * 2014-12-22 2021-02-10 Norner Verdandi As Polyethylene for pipes
WO2016196965A1 (en) * 2015-06-05 2016-12-08 Tredegar Film Products Corporation Low microgel surface protection film
US9645131B1 (en) * 2015-12-04 2017-05-09 Chevron Phillips Chemical Company Lp Polymer compositions having improved processability and methods of making and using same
US9645066B1 (en) * 2015-12-04 2017-05-09 Chevron Phillips Chemical Company Lp Polymer compositions having improved processability and methods of making and using same
US11230614B2 (en) * 2017-02-03 2022-01-25 Exxonmobil Chemical Patent Inc. Methods for making polyethylene polymers
EP3630879B1 (en) * 2017-05-25 2023-08-30 Chevron Phillips Chemical Company LP Methods for improving color stability in polyethylene resins
US20210238323A1 (en) 2018-06-13 2021-08-05 Univation Technologies, Llc Bimodal polyethylene copolymer and film thereof
EP3844194A1 (en) * 2018-08-29 2021-07-07 Univation Technologies, LLC Bimodal polyethylene copolymer and film thereof
CN112638962B (en) 2018-09-28 2023-05-16 尤尼威蒂恩技术有限责任公司 Bimodal polyethylene copolymer compositions and pipes made therefrom
US20220325083A1 (en) 2019-09-26 2022-10-13 Univation Technologies, Llc Bimodal polyethylene homopolymer composition
EP4048503A1 (en) 2019-10-23 2022-08-31 Nova Chemicals (International) S.A. Biaxially oriented mdpe film
BR112023003324A2 (en) 2020-09-22 2023-04-04 Dow Global Technologies Llc BMODAL COPOLYMER, FILM AND METHOD FOR MAKING A BLOWN FILM

Citations (24)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4210142A (en) * 1977-10-22 1980-07-01 Hans Worder Twin chamber injection syringe
US4289729A (en) * 1979-07-26 1981-09-15 Ashland Oil, Inc. Biased degasser for fluidized bed outlet
US4414369A (en) * 1977-08-17 1983-11-08 Nippon Oil Company, Limited Continuous process for the preparation of polyolefins having widely distributed molecular weights
US4461873A (en) * 1982-06-22 1984-07-24 Phillips Petroleum Company Ethylene polymer blends
US4547551A (en) * 1982-06-22 1985-10-15 Phillips Petroleum Company Ethylene polymer blends and process for forming film
US4551704A (en) * 1983-09-27 1985-11-05 International Business Machines Corporation Look-back analog to digital converter
US5260384A (en) * 1991-09-06 1993-11-09 Nippon Petrochemicals Company, Ltd. Polyethylene composition
US5284613A (en) * 1992-09-04 1994-02-08 Mobil Oil Corporation Producing blown film and blends from bimodal high density high molecular weight film resin using magnesium oxide-supported Ziegler catalyst
US5378764A (en) * 1992-10-08 1995-01-03 Phillips Petroleum Company Polyethylene blends
US5494965A (en) * 1993-03-26 1996-02-27 Borealis Polymers Oy Process for manufacturing olefin polymers and products prepared by the process
US5514455A (en) * 1994-07-08 1996-05-07 Union Carbide Chemicals & Plastics Technology Corporation Film extruded from an in situ blend of ethylene copolymers
US5539076A (en) * 1993-10-21 1996-07-23 Mobil Oil Corporation Bimodal molecular weight distribution polyolefins
US5681523A (en) * 1994-05-09 1997-10-28 The Dow Chemical Company Medium modulus polyethylene film and fabrication method
US5739266A (en) * 1994-08-30 1998-04-14 Bp Chemicals Limited Process for modifying a polyethylene in an extruder
US5858491A (en) * 1994-11-02 1999-01-12 Dow Belgium Hollow molded articles and process for manufacturing them
US5882750A (en) * 1995-07-03 1999-03-16 Mobil Oil Corporation Single reactor bimodal HMW-HDPE film resin with improved bubble stability
US6201078B1 (en) * 1995-04-28 2001-03-13 Solvay Polyolefins Europe-Belgium Ethylene polymer and processes for obtaining it
US6316546B1 (en) * 1991-03-06 2001-11-13 Exxonmobil Oil Corporation Ethylene polymer film resins
US6355733B1 (en) * 2000-10-13 2002-03-12 Equistar Chemicals, Lp Polyethylene blends and films
US6485662B1 (en) * 1996-12-03 2002-11-26 Union Carbide Chemicals & Plastics Technology Corporation Process for preparing a simulated in situ polyethylene blend
US6534604B2 (en) * 1999-10-22 2003-03-18 Univation Technologies, Llc Catalyst composition, method of polymerization, and polymer therefrom
US6545093B1 (en) * 1998-10-27 2003-04-08 Basell Polyolefine Gmbh High mixture-quality bi-modal polyethylene blends
US6562905B1 (en) * 1998-04-06 2003-05-13 Borealis Technology Oy High density polyethylene compositions, a process for the production thereof and films prepared
US6579922B2 (en) * 1999-03-30 2003-06-17 Fina Research, S.A. Polyolefins and uses thereof

Family Cites Families (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4289727A (en) 1979-12-19 1981-09-15 Mobil Oil Corporation Method for extrusion of tubular films
JPS581708A (en) 1981-06-25 1983-01-07 Mitsubishi Chem Ind Ltd Production of polyolefin
US4855370A (en) 1986-10-01 1989-08-08 Union Carbide Corporation Method for reducing sheeting during polymerization of alpha-olefins
US5210142A (en) 1992-02-13 1993-05-11 The Dow Chemical Company Reduction of melt fracture in linear polyethylene
JP3474888B2 (en) * 1993-02-09 2003-12-08 三菱製紙株式会社 Method for producing polyethylene resin-coated paper
JP3167822B2 (en) * 1993-03-05 2001-05-21 三菱製紙株式会社 Method for producing polyethylene-based resin-coated paper
US6420298B1 (en) * 1999-08-31 2002-07-16 Exxonmobil Oil Corporation Metallocene catalyst compositions, processes for making polyolefin resins using such catalyst compositions, and products produced thereby
CN1264866C (en) 2001-05-07 2006-07-19 埃克森美孚化学专利公司 Polyethylene resins
JP4426300B2 (en) 2001-11-30 2010-03-03 ユニベーション・テクノロジーズ・エルエルシー Oxygen tailoring of polyethylene resin

Patent Citations (24)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4414369A (en) * 1977-08-17 1983-11-08 Nippon Oil Company, Limited Continuous process for the preparation of polyolefins having widely distributed molecular weights
US4210142A (en) * 1977-10-22 1980-07-01 Hans Worder Twin chamber injection syringe
US4289729A (en) * 1979-07-26 1981-09-15 Ashland Oil, Inc. Biased degasser for fluidized bed outlet
US4461873A (en) * 1982-06-22 1984-07-24 Phillips Petroleum Company Ethylene polymer blends
US4547551A (en) * 1982-06-22 1985-10-15 Phillips Petroleum Company Ethylene polymer blends and process for forming film
US4551704A (en) * 1983-09-27 1985-11-05 International Business Machines Corporation Look-back analog to digital converter
US6316546B1 (en) * 1991-03-06 2001-11-13 Exxonmobil Oil Corporation Ethylene polymer film resins
US5260384A (en) * 1991-09-06 1993-11-09 Nippon Petrochemicals Company, Ltd. Polyethylene composition
US5284613A (en) * 1992-09-04 1994-02-08 Mobil Oil Corporation Producing blown film and blends from bimodal high density high molecular weight film resin using magnesium oxide-supported Ziegler catalyst
US5378764A (en) * 1992-10-08 1995-01-03 Phillips Petroleum Company Polyethylene blends
US5494965A (en) * 1993-03-26 1996-02-27 Borealis Polymers Oy Process for manufacturing olefin polymers and products prepared by the process
US5539076A (en) * 1993-10-21 1996-07-23 Mobil Oil Corporation Bimodal molecular weight distribution polyolefins
US5681523A (en) * 1994-05-09 1997-10-28 The Dow Chemical Company Medium modulus polyethylene film and fabrication method
US5514455A (en) * 1994-07-08 1996-05-07 Union Carbide Chemicals & Plastics Technology Corporation Film extruded from an in situ blend of ethylene copolymers
US5739266A (en) * 1994-08-30 1998-04-14 Bp Chemicals Limited Process for modifying a polyethylene in an extruder
US5858491A (en) * 1994-11-02 1999-01-12 Dow Belgium Hollow molded articles and process for manufacturing them
US6201078B1 (en) * 1995-04-28 2001-03-13 Solvay Polyolefins Europe-Belgium Ethylene polymer and processes for obtaining it
US5882750A (en) * 1995-07-03 1999-03-16 Mobil Oil Corporation Single reactor bimodal HMW-HDPE film resin with improved bubble stability
US6485662B1 (en) * 1996-12-03 2002-11-26 Union Carbide Chemicals & Plastics Technology Corporation Process for preparing a simulated in situ polyethylene blend
US6562905B1 (en) * 1998-04-06 2003-05-13 Borealis Technology Oy High density polyethylene compositions, a process for the production thereof and films prepared
US6545093B1 (en) * 1998-10-27 2003-04-08 Basell Polyolefine Gmbh High mixture-quality bi-modal polyethylene blends
US6579922B2 (en) * 1999-03-30 2003-06-17 Fina Research, S.A. Polyolefins and uses thereof
US6534604B2 (en) * 1999-10-22 2003-03-18 Univation Technologies, Llc Catalyst composition, method of polymerization, and polymer therefrom
US6355733B1 (en) * 2000-10-13 2002-03-12 Equistar Chemicals, Lp Polyethylene blends and films

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20090246433A1 (en) * 2004-12-17 2009-10-01 Michie William J Rheology modified relatively high melt strength polyethylene compositions and methods of making pipes, films, sheets, and blow-molded articles
US8920891B2 (en) 2004-12-17 2014-12-30 Dow Global Technologies Llc Rheology modified relatively high melt strength polyethylene compositions and methods of making pipes, films, sheets, and blow-molded articles
US20100105849A1 (en) * 2007-03-30 2010-04-29 Univation Technologies, Llc Systems and methods for fabricating polyolefins
US8981021B2 (en) 2007-03-30 2015-03-17 Univation Technologies, Llc Systems and methods for fabricating polyolefins
CN105086095A (en) * 2014-04-24 2015-11-25 中国石油化工股份有限公司 Polyethylene composition and preparation method thereof, and gas permeable film prepared from polyethylene composition

Also Published As

Publication number Publication date
WO2005061561A1 (en) 2005-07-07
KR101085329B1 (en) 2011-11-23
MXPA06006403A (en) 2006-08-23
MY137613A (en) 2009-02-27
PL1692195T3 (en) 2009-06-30
EP1692195A4 (en) 2007-05-23
BRPI0417355A8 (en) 2018-05-08
AU2004303753A1 (en) 2005-07-07
JP4662946B2 (en) 2011-03-30
ATE421543T1 (en) 2009-02-15
AU2004303753B2 (en) 2009-08-13
BRPI0417355A (en) 2007-03-13
US7101629B2 (en) 2006-09-05
RU2349611C2 (en) 2009-03-20
US6878454B1 (en) 2005-04-12
US20050153148A1 (en) 2005-07-14
EP1692195B1 (en) 2009-01-21
US7090927B2 (en) 2006-08-15
DE602004019245D1 (en) 2009-03-12
JP2007513236A (en) 2007-05-24
CN1890271A (en) 2007-01-03
EP1692195A1 (en) 2006-08-23
TWI342883B (en) 2011-06-01
KR20060109930A (en) 2006-10-23
BRPI0417355B1 (en) 2014-03-11
AR045633A1 (en) 2005-11-02
CA2546368A1 (en) 2005-07-07
RU2006123706A (en) 2008-01-20
CN1890271B (en) 2011-05-04
TW200523302A (en) 2005-07-16
ES2320142T3 (en) 2009-05-19

Similar Documents

Publication Publication Date Title
US7090927B2 (en) Polyethylene films
US8920891B2 (en) Rheology modified relatively high melt strength polyethylene compositions and methods of making pipes, films, sheets, and blow-molded articles
RU2444546C2 (en) Polyolefin compositions, articles made therefrom and preparation methods thereof
US6995235B1 (en) Methods of producing polyolefins and films therefrom
US11142599B2 (en) Ethylene copolymer having enhanced film properties
ZA200604493B (en) Polyethylene films
LT et al. RHEOLOGIEMODIFIZIERTE POLYETHYLENZUSAMMENSETZUNGEN COMPOSITIONS DE POLYETHYLENE A RHEOLOGIE MODIFIEE

Legal Events

Date Code Title Description
REMI Maintenance fee reminder mailed
LAPS Lapse for failure to pay maintenance fees
STCH Information on status: patent discontinuation

Free format text: PATENT EXPIRED DUE TO NONPAYMENT OF MAINTENANCE FEES UNDER 37 CFR 1.362

FP Lapsed due to failure to pay maintenance fee

Effective date: 20100815